Welcome to our list of things that are flat!
Flat refers to a surface which is consistent and uniform, but can also refer to things that are boring or uninteresting
We’ve done our best to cover as many different items with as many different contexts as possible with this list, so we hope you find what you need!
Here’s a visual list of things that are flat:
We hope that visual list of flat things was useful!
Here’s a longer and more descriptive list of things that are flat:
Paper: This is a thin material made from wood pulp used for drawing, writing, decorating and origami
Postcard: This is a thick, flat card with a decoration on one side which is used to send short messages to people
Stamps: These are small, rectangular pieces of sticky paper used to indicate that mail has been paid forTape: Tape is an adhesive used to hold things together
Envelope: These are flat paper rectangles used to store and send mail
Bookmark: Bookmarks are thin, flat objects used to mark a person’s place in their reading material
Tissue: These are thin, flat rectangles used to clean up or absorb small messes
Streamer: Streamers are long, wide crepe ribbons used for home decoration (usually only for parties or celebrations)
Business Card: These are small cards with work contact details on them used for socially connecting business people
Flash Cards: Flash cards are thick, lined paper cards that are used as a study aid
Playing Cards: These can be made of paper or plastic, and are used for playing games like solitaire and poker
Stencil: This can refer to either a thin plastic sheet with parts carved out of it, or the artwork/lettering that is made using the stencil
Poster: A poster is a large-scale graphic, usually used in advertising
Tarot Card: Tarot cards are longer and narrower than normal playing cards, and are used to study one’s feelings and thoughts and how they may affect the future
Name Tag: These are small cards with names written on them, used at social and business events
They can be made of paper, card, or plastic
Price Tag: These are small cardboard tags left on products to marks prices and names
Map: Even though we usually navigate by GPS, paper maps still exist and express geography on a flat suface
Tickets: Tickets can be in digital or paper form
Gift Wrap: This is a thin, decorative paper used to wrap gifts
These days, large cloths can be used as a more eco-friendly, re-suable alternative
Recipe: Many recipes can be found online, but recipes were traditionally shared written or printed on paper
Label: These are small stickers used to give information about the object it’s adhered to
Photos: These are printed on photo paper, which is thicker than normal printing paper (80gsm) but still very flat
Bumper Sticker: These are generally wide, short stickers meant for sticking on one’s car
They generally show short, witty idioms, political leanings or brand affiliations
Confetti: Confetti is a bundle of small, thin pieces of coloured paper, meant to flutter decoratively through the air when thrown
Ribbon: These are long, thin strips of fabric used as decorative ties
Gift Card: These are generally small plastic or paper cards which hold information about pre-paid gifts
Library Card: These are cards used to store information about books that a person has borrowedPressed Flowers: Flowers can be pressed by placing them between absorbent paper and a few heavy weights
This dries and preserves them and results in a dry, flat flower
Stickers: These are small pieces of paper that have adhesive on one side
CD: These are flat, thin discs that are used to play music
Money: Money is generally printed onto paper or paper-like material and is light and thin for portability
Pamphlet: Pamphlets are folded pieces of large paper used to convey sections of information
Sign: These are used to quickly convey a small amount of information, and are usually used in large public areas with a high amount of traffic
Napkin: Napkins are thicker than tissues, but have the same basic purpose (to absorb small spills)Band-Aid: These are small adhesive strips with a pad of gauze in the middle to protect scratches and small cuts or wounds
Rolled Oats: Usually eaten as a breakfast food, these are flat grains known for their high protein content
Chopping Board: A flat, thick, durable board used to protect tables while cutting food
Tie: A long strip of fabric intended to be tied in decorative knots around the neck, usually only while also wearing a suit
Camera Film: A thin, flexible plastic used for developing photographs
Greeting Card: These are folded-over pieces of card to show sentiment for special milestones, like retirement, graduating or birthdays
Floor: While floors may be tilted, sloped, or have stairs, they generally will still have a flat surface for safety and ease of use
Mirror: A flat, reflective surface that allows us to see our reflection
Floppy Disc: An old and now obsolete way of storing digital files and data
Phone: While phones were not always thin and flat, today’s phones generally consist of a large screen with the smallest amount of buttons possible
iPod: iPods have always been known for their flat, simple, minimalist designs
Weaving: These are knotted pieces of art, generally used as wall hangings
Ruler: Used for measuring small distances, usually between 30cm and one metre
Window: A transparent plate of glass used to let light into buildings
TV: TVs in the past have been more chunky and rounded, but TVs today are thin and so flat that they went through a period of being called “flatscreen TVs”Tile: These are small plates of ceramic used to protect a surface in a decorative, practical way
Knife: These are blades intended to cut or separate objects
Scalpel Blade: This is an extremely thin and sharp version of a knife, generally used for delicate incisions
Tape Measure: A long, thin, flexible ribbon used to measure objects
Collage: A collage is a piece of art that is composed of layered pieces of found items, like magazine clippings, letters or coloured paper
Poker Chips: These are small round tokens used to represent money in a poker gameWhiteboard: These are large, glossy boards used in classrooms
Carpet: Carpets are furry floor coverings that get dirty easily, but keep a room warm
Canvas: This is a thick, sturdy cloth used as a painting surface
Cloth: This is a generally soft and flexible material made of woven fibres
Fabric: This is another term for cloth, and is generally used interchangeably
Zine: A very short, handmade and hand printed publication, usually of an extremely limited run
It’s a wooden board that comes in varying sizes and thicknesses
Tablet: Tablets are thin, flat computers that look like a computer screen without the keyboard
Laptop: A laptop is a portable computer that is flat when folded
Painting: A painting is an art medium that generally results in flat, 2d work on canvas or paper
Drawing: This is a form of artistic expression where marks are made on canvas or paper
Desk: These are pieces of furniture that have a flat surface to store items, write and draw
Clothes: These are made to protect and decorate our bodies and are composed of generally flat pieces of cloth
Book: A book is made up of at least a hundred flat pages
Rug: This is a flat weave used to warm and decorate a room
Belt: These are long, wide ribbons of tough, durable materials used to hold pants up
Road: The surface that cars travel on
While they might be hilly or sloped, their surface is overall flat
Chiclet Keys: A keyboard where the keys are flat, square-shaped and with space between them for easy cleaning
Notebook: A slim book with lined paper, intended to be used for writing
Scale: A flat device that measures weight
Box: A sealable structure used to store objects to be transported or organised
Usually made of cardboard, plastic or metal
Pillowcase: Protective pillow covers, made of thin, soft fabric
Flatpack Furniture: This is disassembled furniture that’s been packed as densely and flat as possible for ease of transportation
Leaves: While leaves come in many shapes, sizes and textures, many have a generally flat shape
Usually used in woodworking
Saw: A wide blade with large, serrated teeth
Spatula: A thin, flexible blade that is used to scoop and shape in cooking and baking
Fondant: A dense, firm icing that is used to decorate the tops of cakes
While fondant can hold its own shape and is therefore used for edible sculptures, it’s most commonly rolled out flat and used in sheets
Icing: A sweet confection made of butter and sugar
Most commonly used to decorate the flat tops of cakes
Rice Cakes: These are large, round crackers made of puffed rice pressed together in a cake
Crackers: These are thin, almost wafer-like biscuits made of mixed grains
Door: While doors can have panels and decorative carvings in and on them, their overall profile is flat
Plate: A flat surface for eating food, as opposed to a bowl
Platter: This is a very large plate used for serving more than one person
Tray: A large board with raised edges and handles for holding multiple items on a flat surface
Bed: An appropriately flat, soft surface to sleep on
Mattress: This is the thick, spongy surface that you place on top of a bed frame
Foil: This is very thin aluminium commonly used to keep food warm and protected
Baking Paper: This is waxed paper used to keep food fresh and protected from bacteria
Fruit Leather: This is a sweet, sugary snack made of pressed fruit pulp in the shape of a belt
Pop Tart: This is a flat, rectangular pastry filled with jam or icing
Sliced Bread: Slicing bread gives it a flat shape
Toast: Toast is only made with flat, sliced bread
Yoga Mat: These are thin panels of foam used to cushion a person’s joints from the floor when practising yogaSword: Mostly composed of thin, hammered pieces of metal
Rock: Many rocks and cliff faces are flat but can be worn smooth by wind and water
Usually enjoyed as a breakfast food
Crepe: Thin French pancakes that are eaten in both sweet and savoury styles
Tortilla: Round, flat bread used to make tacos and kebabs
Pita Bread: Round, flat Lebanese bread used to make wraps
Towel: Fluffy cloth used to dry a person’s body after a shower
Pasta:While pasta comes in many forms, shapes and sizes, it is generally first rolled out into flat sheets
Pastry Sheet: Flat sheets of pastry are usually available frozen for ease of use
Pizza Box: Flat boxes used to transport pizza neatly and easily
Notepad: A slim wad of lined paper used to take written notes
Table: Tables need to have flat surfaces in order to hold objects on them without rolling off onto the floor
Placemat: Flat panels made of plastic, metal, fabric, cardboard or cork used to protect a table’s surface from hot food while eating
Roti: This is a flat indiant bread cooked in a pan and usually eaten with curry
Sour Strap: This is a candy in the shape of a wide, thin belt and covered with large sugar crystals
Lilypad: Large round leaves that float on the surface of ponds
Mousepad: A small, flat surface for computer mice to rest on while being usedUsing a mousepad helps a mouse track better
Post Its: While these are now available in many shapes and sizes, the classic post-it notes are small coloured squares with a strip of tacky adhesive on one side
Stretcher Bar: These are wooden bars, usually cedar or pine, that can be slotted together to have canvas stretched over ready for painting
Mounting Board: This is a thick, sturdy cardboard available in many colours and sizes used to mount photos when being framed
Sketchbook: A slim book of blank, unlined paper, used for drawing
Hard Drive: These are small gadgets used to store extra data
Field: A wide expanse of outdoor area where grains are commonly grownTennis Court: A flat area where tennis games are played
Screen: While curved screens are newly available, screens of all types have historically been flat
Serving Plate: A large plate, similar to a platter
Palette: These can be in reference to two things (both of which are flat) – a board for mixing paints on, and a kit of eyeshadow pans
Note (music): If a note is played slightly lower in tone than the intended note, then it’s called a “flat” note
Blanket: A soft, flexible material used to keep warm by insulting body heat
Swatch: A small block of painted colour, used to show people what paint will look like when dry
Frisbee: A disc used for sports and recreation, usually made of plastic of rigid foam
Saucer: A small ceramic disc used with teacups
Game Cartridge: These are flat cartridges that have games and saved game information in them
Wafer: Very light, airy biscuits with icing layered between them
Mint Thin: A thin biscuit topped with mint fondant and covered in dark chocolate
Chocolate Bar: A piece of chocolate in a bar shape
Partition: A large panel or set of panels used to separate an area into sections
Wooden Plank: A cut piece of wood in a wide bar shape
Perspex: Transparent plastic used to make architecture models and jewelry
Popsicle Stick: A narrow piece of wood used as a handle for popsicles and other iced treats
Watercolour: Watercolour is a very thin medium, leading to flat paintings
Watercolour Pan: These are rectangular containers filled with dry watercolour paint, ready to be used when wet
Biscuit: While biscuits can come in any shape or size, they tend to be flat as they have no rising agents in their ingredient list
Pie: A pastry filled with savoury ingredients, eaten when hot
Discworld: This is a fictional world created by Terry PratchettTablecloth: A thin cloth used to cover a table to protect it from dirt and spills when eating
Bath Mat: A mat placed on the floor in a bathroom to prevent slipping on the wet floor after a showerRoomba: A small autonomous vacuum which is circular and flat in shape
Tyre: When a tyre is low on oxygen, it’s referred to as a flat tyre
Anvil: An anvil is a strong, metal surface used in metalworking
Badge: A small icon attached to a pin, used as decoration on clothing and backpacks
Manta Ray: Flat marine life with “wings”Sting Ray: Similar to manta rays, but with a different shape
Flounder: A type of flat fish
Turbot: A type of flat fishDeflated Balloon: When not filled with air, balloons become shapeless and flat
Soft Drink: If a soft drink loses its carbonation and fizziness, it’s referred to as flat
Hair: If hair is oily, it can look flat
Attitude: When lacking enthusiasm, an attitude can be called flatX-Ray: A flat piece of film used to investigate our skeletonAtmosphere: If an atmosphere is lacking in energy and enthusiasm, it’s called a flat atmosphere
Tone of Voice: Without energy or enthusiasm, a tone of voice is flatPerformance: If a performance misses the mark, it’s called a flat performance
We hope this list of flat things was useful and that you found what you needed
While we did our best to cover all of the varied meanings of “flat” in this list, we may have missed something out – so feel free to let us know and leave a comment if you know of something that should be included
Welcome to our list of things that are fragile!
Fragile things are those which can break or shatter easily
They are usually thin, with delicate joints, or made out of a very soft or brittle material
Our list covers objects, animals, food and more, so we hope you find what you’re looking for here!
Here’s a visual list of things that are fragile:
Hopefully that visual list of fragile things was useful!
Here’s a longer and more descriptive list of things that are fragile:
Silence: Easily broken by any type of noiseSnowflake: These are delicate formations of ice crystalsBubble: As soon as part of a bubble becomes dry, it can pop
While they are flexible and strong for their width and size, to humans they are very easily brokenDragonfly: A small, thin insect with extremely thin, transparent wings
Fly: A small, light insect with multi-faceted eyes and transparent wingsBee: Insects that are famous for making honey and for their black and yellow striped bodies
They have thin, delicate legs and transparent wings
Pastel: These are very fragile art materials made of pigment held together by a binder
Chemically preserved flowers are very soft, and can last a few years with careHouse of Cards: A common game with playing cards is to build a vertical, self-standing structure
Snail Shell: Snail shells are known for being delicate and fragile
Pastry: Baked goods typically made with butter, sugar and egg
Tea Leaves: Tea leaves are dried before use, making them brittle and easy to break
Icing: When warm, icing (also known as frosting) can melt and collapse easily, and is very soft to the touch
When it’s cooled, it’s still easy to dent and leave marks in
Light Bulb: Generally made of thin glass, which is prone to breaking if dropped
Is typically eaten as a quick snack, or broken up into smaller pieces to use as a topping
Dried Leaves: When leaves die and fall off trees, they become fragile and brittle
They are notorious for being easy to break and tear
Fairy Floss: A type of candy made from spun sugar
Wafer: A thin, crisp, sweet biscuit
Love Letter Biscuits: These are very thin wafers that have been rolled into a cylinder and are filled with a flavoured icing
Croissant: A type of flaky pastry with many thin, pliable layers
Lindt Balls: A truffle chocolate that consists of a thin shell of solid chocolate housing liquid chocolateMeringue: A sweet dessert typically made from egg whites, but can also be made with chickpea water
Is easily broken in to pieces
Filo Pastry: Thin sheet pastry that is commonly used by layering many sheets
Shortcrust: A sort of buttery pastry with a “short” texture (meaning it’s easily broken down/apart)Egg Yolk: Egg yolks have a very fragile membrane keeping their shape
Tissue: A thin, soft paper used for wiping up small spills or bodily fluids
They are soft, easily bruised, and easily torn away from the body of the flower
Wafer Cone: Cones used to hold ice cream
Paper: A thin material made from wood
Easily folded and torn
Plates: A flat, usually round surface used for holding non-liquid foods
Bowl: A round, domed surface for holding food
Usually made of glass, porcelain, ceramic or other easily breakable materials
Mango: A soft, sweet tropical fruit which is easily bruised
Berries: Small, sweet fruits which are soft and easy to damage
Has a nebulous form which is easily broken apart
Rice Paper: Rice paper comes in two forms – a thin, translucent edible paper used to wrap foods and a thin, translucent decorative paper
Tissue Paper: A lightweight, translucent paper which is used for wrapping and other decorative purposes
Lace: A delicate, ornate fabric made of thin yarn or threads that are woven together in an open web-like figure
Cup: A round, domed container used to hold liquids
Commonly made from easily breakable materials like glass, ceramic, china or porcelain (although it comes in plastic varieties too)
Biscuit: Baked goods that are brittle and easily broken, crumbled or snapped apart
Piggy Bank: While many piggy banks are in the form of metal tins or plastic containers, the stereotypical idea of a piggy bank is a porcelain pig that is smashed open when the funds inside are needed
Ring: While rings are generally intended for long-term wear, they are fairly fragile items
Earring: Since earrings are made of multiple parts (post, end, screw, any jewels) and are so small and delicate, they are easy to break and should be handled with care
Necklace: A type of jewelry that is worn around the neck
Generally consists of a thin chain and some sort of pendant
Pendant: A decorative piece that hangs on a chain necklace
Usually a carved piece of gold or silver, or some sort of set jewel
Bracelet: Bracelets are small, usually thin, delicate and made of many connected parts
Bangle: While bangles structurally have more integrity than a bracelet, they are easy to bend out of shape
Plants: Plants can be damaged by many things – they can be burnt by sunlight, drowned by too much water, knocked over by careless people or wind, and their leaves and petals are easily bruised, bent and torn
Potpurri: These are scented, dried flower petals (usually fragrant flowers like roses or lavender) that are bundled together in cloth and used as a perfume for small areas
Teapot: A piece of pottery which is used to brew tea leaves and make tea
Teeth: While unpleasant to think about, teeth are easily broken, chipped, cracked or scratched
Macaron: These are fragile sweets consisting of two meringue-based cookies sandwiched together
Vase: These are containers used to hold fresh flowers (or fake ones)
Usually made of glass, ceramic or porcelain
Crackers: A flat, thin, baked bisuit which is usually flaky and brittle
Frog: Frogs are very soft and have easily squashed bodies
Their skin is also very thin and can be torn if you touch them with dry fingers (so please don’t handle frogs that you see in the wild unless they need help and you have wet hands! )Baby: Depending on age, babies can be very delicate as their bones and muscles aren’t yet fully developed
Mirror: Mirrors are made of glass, which makes them very delicate
Creme Brulee: A sweet dessert with a thin, fragile layer of burnt sugar on topProfiterole: Thin, flaky cream puffs topped with a thin layer of chocolate
Canvas Artwork: Depending on the type of paint used, canvas artworks can be brittle nad flaky
Choux Pastry: A type of light pastry dough
Flaky Pastry: Also known as blitz pastry or rough puff
A type of pastry that is very light and flaky
Puff Pastry: A light pastry made of laminated dough that puffs up when baked
Cake: A sweet baked good that is very soft and spongy
Skin: Skin is easily pliable and while unpleasant to think about, is easily scratched, cut, broken and torn
Balsa Wood: A very soft type of wood which is commonly used in model-making and architectural projects
Phone Screen: Higher-end phones tend to have screens made of glass, which is easily shattered or cracked when the phone is dropped
Trust: Easily broken with a lie or insecurities
Ocarina: These are a small instrument similar to a large, oval-shaped whistle
Produces mellow tones and is usually made of ceramic
Glass Bottle: While recyclable, these bottles are more fragile than plastic and should be handled with care
Jar: Commonly made of either glass or plastic
Tabla: A type of round drum that is played with the fingertipsWindow: Windows are made of glass and have to be reinforced so they aren’t so easily broken or smashed
Pretzel: These are long, thin, baked biscuits formed in a curled shape
Since they are crispy and baked, they are easily snapped and shattered
Books: Books are filled with pages of delicate paper that are easy to bend and mark
Earphones: Earphones can have long, thin cables which tangle easily and can become detached
Cables: Electrical cables and wires, while reinforced and strengthened, can still be easily tangled and come apart from their plugs
Glass: A transparent material used in tableware, windows, lenses and optics
Potato Chips: Thinly cut potato chips are very brittle and fragile
Keyboard: These are a tool for typing out information on a computer
They have many moving parts and electronics within, so can be damaged by dropping them or spilling food or water on them
Ceramic: A type of baked clay which is used to make pots, cups, bowls and vases
Porcelain: A type of cermamic which is known for its toughness and translucence
Still easy to break
Computer Mouse: These days mice use laser tracking rather than a rubber ball
The electronics and multiple parts can make them more fragile than other equipment one might use
Fountain Pen: High-quality fountain pens have nibs made of gold, which is soft and easy to bend or break
Violin: Violins are made of thin pieces of wood and a bridge that is held largely with gravity and friction
They are a very delicate instrument
Guitar: Made of thin pieces of wood, which can warp and flex depending on the temperature and humidity of the area it’s in
CDs: A now essentially obsolete way of storing and playing music
Ukulele: Looks like a miniature guitar, but with four strings instead of six
Climate: Climates are difficult to manage and maintain, especially when it’s already in a bad state (like ours)
We hope this list of fragile things was useful and that you found what you needed!
We did our best to cover all of the varied meanings of “fragile” with our visual gallery of fragile things and descriptive list
From a human’s perspective, small can be anything from a single cell organism to miniature replicas of much larger things
But then, the protons, electrons, and neutrons opened a whole new world on the smallest scale
And just as we started to entertain the thought that these are fundamental particles, researchers showed that neutrons and protons themselves are made of multiple quarks
So, as far as we know, quarks and leptons (a family of elementary particles that include electrons) are the smallest, most fundamental matter in the universe
Below is a list of the smallest things
Smallest Cannon
According to the Guinness World Records, the world’s smallest working cannon (15 µm x 5 µm x 5 µm) was designed by a group of researchers, including Stuart Ibsen, Joseph Wang, and Sadik Esener, among others
Smallest Gun
The record for the world’s smallest (functional) revolver goes to Miniature Revolver C1ST
Smallest Surviving Infant
Weighing at just 245 grams at the time of the birth, Akel or Saybie, as the doctors and nurses nicknamed her, is the world’s smallest surviving infant
A pregnancy usually lasts for 40 weeks or 9 months
9 Smallest Production Car
The world’s smallest car, the Peel P50 is a three-wheeled, single-seater microcar, which was initially manufactured by the Peel Engineering Company in the 1960s for commercial purposes
Read: 12 Smallest Stars in the Universe
8 Smallest Fish
A mature male specimen of the Photocorynus spiniceps, an anglerfish species, can measure anywhere between 62 to 73 millimeters in length
It is the smallest known of all mature fish species and vertebrates
spiniceps, exhibit a unique behavior known as parasitism, in which smaller males depend on much larger females for their overall survival
7 Smallest Horse
World’s smallest horse
Standing at just 567 cm, Bombel (“Bubble”) is the current smallest male horse in the world
At a young age, when Bombel was just two months old, he looked smaller even for a miniature horse
The smallest horse ever was Thumbelina (43 centimeters), who died back in 2018
6 Smallest Computer
Cross-section of the M3 computer | Image Courtesy: Electrical & Computer Engineering, University of Michigan
In 2015, the University of Michigan unveiled the world’s smallest computer, Michigan Micro Mote (M3), measuring at just half a centimeter
Each M3 computer features as much as eight layers that carry out different functions
Currently, the device has a small effective range of about 2 meters
If you’re wondering about small personal computers that you can actually buy, then there are a couple of options
Read: The Smallest Spectrometer Ever Built | Made Of Single Nanowire
5 Smallest Primate
With an average body length of 95 centimeters, Madame Berthe’s mouse lemur, or simply Berthe’s mouse lemur, is the world’s smallest primate
Read: World’s Smallest House | About 20 Micrometer Long
4 Smallest Radio
In 2007, a team of researchers from the University of California, Berkeley designed one of a kind radio receiver out of a carbon nanotube measuring just 100 micrometers in length and 10 micrometers in diameter
It remains the world’s smallest radio to date
Here, all the functions are carried out by a single nanotube together with two electrodes, between which it is placed
Read: World’s Smallest, Single Atom Transistor That Works At Room Temperature
3 Smallest Camera (Image Sensor)
World’s smallest camera | Image Courtesy: OmniVision
The record for the world’s smallest camera goes to OmniVision OV6948, developed by OmniVision Technologies Inc, a California based digital imaging products
It has a resolution of 200 x 200, with each pixel size just 175 µm across and generates color images using an RBG Bayer filter
The OmniVision OV6948 is designed to operate inside the smallest of places and something as intricate as human veins
2 Smallest Atom
Once thought the smallest thing in the universe, atoms were created shortly (on a cosmic scale) after the Big Bang
Atoms are made up of three particles; protons and neutrons, which are composed of much smaller quarks, and electrons
In terms of mass, the smallest atom known to us is a hydrogen atom, which has one electron and one proton
1 Smallest Particle
We have already established that quarks and electrons are the smallest known particles in the universe
So far, researchers have been able to identify six types or flavors of quarks, namely, up (u), down (d), charm (c), strange (s), top (t), and bottom (b)
Multiple quarks bond together to form a subatomic composite particle known as hadron
Protons and neutrons are the two most common types of hadrons that have an odd number of quarks (three), also known as baryons
Read: Scientists Gain Control Of Smallest Unit Of Sound: Phonon
Electrons, unlike protons and neutrons, are elementary are part of a broader group of fundamental particles known as leptons
Electrons are about 1900 times less massive than protons