Welcome to the Boston Astronomy website ...

---

This website has been created by and is supported by a group of Boston, MA - area amateur astronomers. It is intended to be a convenient site to access news and information about astronomy and space-related activities of interest to the community and the public.

---

---

Factor (m)	Multiple	Value	Item
10−35	1 Planck Length	0.0000000000162 ym (1.62×10−35 m)	Planck length; typical scale of hypothetical loop quantum gravity or size of a hypothetical string and of branes; according to string theory lengths smaller than this do not make any physical sense.[2] Quantum foam is thought to exist at this level.
10−24	1 yoctometre (ym)	20 ym (2 × 10−23 metres)	effective cross section radius of 1 MeV neutrinos[3]
10−21	1 zeptometre (zm)		Preons, hypothetical particles proposed as subcomponents of quarks and leptons; the upper bound for the width of a cosmic string in string theory.
		7 zm (7 × 10−21 metres)	effective cross section radius of high energy neutrinos[4]
		310 zm (3.10 × 10−19 metres)	de Broglie wavelength of protons at the Large Hadron Collider (4 TeV as of 2012)
10−18	1 attometre (am)		upper limit for the size of quarks and electrons
			sensitivity of the LIGO detector for gravitational waves
			upper bound of the typical size range for "fundamental strings"[2]
10−17	10 am		range of the weak force

10−15	1 femtometre (fm)	1.5 fm	size of an 11 MeV proton[5]
		2.81794 fm	classical electron radius[6]
			scale of the atomic nucleus[2][7]
10−14	10 fm
10−13	100 fm
10−12	1 picometre (pm)	...	longest wavelength of gamma rays
		2.4 pm	Compton wavelength of electron
		5 pm	wavelength of shortest X-rays
10−11	10 pm	25 pm	radius of hydrogen atom
		31 pm	radius of helium atom
		53 pm	Bohr radius
10−10	100 pm	100 pm (0.1 nm)	1 Ångström (also covalent radius of sulfur atom[8])
		154 pm (0.154 nm)	length of a typical covalent bond (C–C).
		500 pm (0.50 nm)	width of protein α helix
10−9	1 nanometre (nm)	1 nm	diameter of a carbon nanotube[9]
		2.5 nm	Smallest microprocessor transistor gate oxide thickness (as of Jan 2007)
		6–10 nm	thickness of cell membrane
10−8	10 nm	10 nm	thickness of cell wall in gram-negative bacteria[citation needed]
		40 nm	extreme ultraviolet wavelength
		90 nm	Human immunodeficiency virus (HIV) (generally, viruses range in size from 20 nm to 450 nm)
10−7	100 nm	121.6 nm	wavelength of the Lyman-alpha line[10]
		380–435 nm	wavelength of violet light—see color and optical spectrum[11]
		625–740 nm	wavelength of red light[11]

10−6	1 micrometre (µm)	1 µm	also called one micron
		1–3 µm	particle size that a surgical mask removes at 80–95% efficiency[citation needed]
		6-8 µm	diameter of a red blood cell[12]
10−5	10 µm	10 µm	typical size of a fog, mist or cloud water droplet. Chip 10 µm process in 1971.
		12 µm	width of acrylic fibre
		25.4 µm	1/1000 inch, commonly referred to as one thou or one mil
10−4	100 µm	100 µm	average width of a strand of human hair[1]
		200 µm	typical length of Paramecium caudatum, a ciliate protist
		750 µm	maximum diameter of Thiomargarita namibiensis, the largest bacterium ever discovered
10−3	1 millimetre (mm)	2.54 mm	1/10th inch; distance between pins in DIP (dual-inline-package) electronic components
		5 mm	length of average red ant
		7.62 mm	common military ammunition size
10−2	1 centimetre (cm)	1.5 cm	length of a large mosquito
		2.54 cm	1 inch
		4.267 cm	diameter of a golf ball
10−1	1 decimetre (dm)	10 cm	wavelength of the highest UHF radio frequency, 3 GHz
		30.48 cm	1 foot
		91.44 cm	1 yard
100	1 metre	1 m	wavelength of the lowest UHF and highest VHF radio frequency, 300 MHz
		1.7 m (5 feet 7 inches)	average height of a human
		8.38 m	The length of a London Bus (Routemaster)
101	1 decametre (dam)	10 m	wavelength of the lowest VHF and highest shortwave radio frequency, 30 MHz
		33 m	length of longest blue whale measured, the largest animal[13]
		93.47 m	height of the Statue of Liberty (foundation of pedestal to torch)
102	1 hectometre (hm)	100 m	wavelength of the lowest shortwave radio frequency and highest medium wave radio frequency, 3 MHz
		137 m (147 m)	height (present and original) of the Great Pyramid of Giza
		979 m	height of the Salto Angel, the world's highest free-falling waterfall (Venezuela)
103	1 kilometre (km)	1 km	wavelength of the lowest medium wave radio frequency, 300 kHz
		1609 m	1 international mile
		1852 m	1 nautical mile
		8848 m	height of the highest mountain on earth, Mount Everest
104	10 km	10.911 km	depth of deepest part of the ocean, Mariana Trench
		13 km	narrowest width of the Strait of Gibraltar, separating Europe and Africa
		90 km	width of the Bering Strait
105	100 km	111 km	distance covered by one degree of latitude on Earth's surface
		163 km	length of the Suez Canal
		974.6 km	greatest diameter[14] of the dwarf planet[note 2] Ceres

106	1,000 km = 1 megametre (Mm)	2,390 km	diameter of dwarf planet Pluto, formerly the smallest planet category[note 2] of our solar system
		3,480 km	diameter of the Moon
		5,200 km	typical distance covered by the winner of the 24 Hours of Le Mans automobile endurance race
		6,400 km	length of the Great Wall of China
		6,600 km	approximate length of the two longest rivers, the Nile and the Amazon
		7,821 km	length of the Trans-Canada Highway
		9,288 km	length of the Trans-Siberian Railway, longest in the world
107	10,000 km	12,756 km	equatorial diameter of the Earth
		40,075 km	length of the Earth's equator
108	100,000 km	142,984 km	diameter of Jupiter
		299,792.458 km	distance travelled by light in one second
		384,000 km = 384 Mm	Moon's orbital distance from Earth
109	1 million km = 1 gigametre (Gm)	1,390,000 km = 1.39 Gm	diameter of the Sun
		4,200,000  km = 4.2 Gm	greatest mileage ever recorded by a car (A 1966 Volvo P-1800S, still driving)
1010	10 million km	18 million km	approximately one light-minute
1011	100 million km	150 million km = 150 Gm	1 astronomical unit (AU); mean distance between Earth and Sun
		~ 900 Gm	optical diameter of Betelgeuse (~600 × Sun)
1012	1000 million km = 1 terametre (Tm)	1.4 ×109 km	orbital distance of Saturn from Sun
		1.96 ×109 km	estimated optical diameter of VY Canis Majoris (1420 × Sun)
		2.3 ×109 km	estimated optical diameter of NML Cygni (1650 × Sun)
		2.37 ×109 km	median point of the optical diameter of UY Scuti, as of 2014 the largest known star
		5.9 ×109 km = 5.9 Tm	orbital distance of Pluto from Sun
		~ 7.5 ×109 km = 7.5 Tm	outer boundary of the Kuiper belt, inner boundary of the Oort cloud (~ 50 AU)
1013	10 Tm		diameter of our Solar System as a whole[2]
		16.25×109 km = 16.25 Tm	distance of the Voyager 1 spacecraft from Sun (as of Feb 2009), the farthest man-made object so far[15]
		62.03×109 km = 62.03 Tm	estimated radius of the event horizon of the supermassive black hole in NGC 4889, the largest known black hole to date
1014	100 Tm	1.8×1011 km = 180 Tm	size of the debris disk around the star 51 Pegasi [16]
1015	1 petametre (Pm)	~ 7.5 ×1012 km = 7.5 Pm	supposed outer boundary of the Oort cloud (~ 50,000 AU)
		9.46×1012 km = 9.46 Pm = 1 light year	distance travelled by light in one year; at its current speed, Voyager 1 would need 17,500 years to travel this distance
1016	10 Pm	3.2616 light-years (3.0857×1013 km = 30.857 Pm)	1 parsec
		4.22 light-years = 39.9 Pm	distance to nearest star (Proxima Centauri)
		4.37 light-years = 41.3 Pm	as of March 2013, distance to nearest discovered extrasolar planet (Alpha Centauri Bb)
1017	100 Pm	20.4 light-years = 193 Pm	as of October 2010, distance to nearest discovered extrasolar planet with potential to support life as we know it (Gliese 581 d)
		65 light-years = 6.15×1017 m = 615 Pm	approximate radius of humanity's radio bubble, caused by high-power TV broadcasts leaking through the atmosphere into outer space
1018	1 exametre (Em)	200 light-years = 1.9 Em	distance to nearby solar twin (HIP 56948), a star with properties virtually identical to our Sun [17]
1019	10 Em	1,000 light-years = 9.46 Em or 9.46 × 1015 km	average thickness of Milky Way Galaxy[18] (1000 to 3000 ly by 21 cm observations[19])
1020	100 Em	12,000 light-years = 113.5 Em or 1.135 × 1017 km	thickness of Milky Way Galaxy's gaseous disk[20]
	950 Em	100,000 light-years	diameter of galactic disk of Milky Way Galaxy[2]
1021	1 zettametre (Zm)
		50 kiloparsecs	distance to SN 1987A, the most recent naked eye supernova
		52 kiloparsecs = 1.62×1021 m = 1.62 Zm	distance to the Large Magellanic Cloud (a dwarf galaxy orbiting the Milky Way)
		54 kiloparsecs = 1.66 Zm	distance to the Small Magellanic Cloud (another dwarf galaxy orbiting the Milky Way)
		200 kiloparsecs = 6.15 Zm	diameter of the low surface brightness disc halo of the giant spiral galaxy Malin 1
1022	10 Zm	13.25 Zm = 1.4 million light years = 600 kiloparsecs	radius of the diffuse stellar halo of IC 1101, one of the largest known galaxies
		24 Zm = 2.5 million light-years = 770 kiloparsecs	distance to Andromeda Galaxy
		3.26 million light-years =30.8 Zm = 1 megaparsec	1 megaparsec
		50 Zm (1.6 Mpc)	diameter of Local Group of galaxies
1023	100 Zm	300–600 Zm = 10–20 megaparsecs	distance to Virgo cluster of galaxies
1024	1 yottametre (Ym)	200 million light-years = 1.9 Ym = 61 megaparsecs	diameter of the Local Supercluster and the largest voids and filaments.
		300 million light-years = 2.8 Ym = 100 megaparsecs	End of Greatness
		550 million light-years ~170 megaparsecs ~5 Ym	diameter of the enormous Horologium Supercluster [21]
		1 billion light-years = 9.46 Ym =306 megaparsecs	diameter of the Pisces–Cetus Supercluster Complex, the supercluster complex where we live.
1025	10 Ym	1.37 billion light years = 1.3×1025 m = 13 Ym	Length of the Sloan Great Wall, a giant wall of galaxies (galactic filament).[22]
		3.26 billion light years =30.8 Ym = 1 gigaparsec	1 gigaparsec
		4 billion light years =37.84 Ym	Length of the Huge-LQG, a group of 73 quasars
1026	100 Ym	1×1010 light-years = 9.5×1025 m = 95 Ym	estimated light travel distance to certain quasars length of the Hercules-Corona Borealis Great Wall, a colossal wall of galaxies, the largest and the most massive structure in the observable universe as of 2014
		13.42 billion light years =1.27×1026 m = 127 Ym	Estimated light travel distance to UDFj-39546284, the most distant object ever observed
		9.2×1010 light years = 8.7×1026 m = 870 Ym	approx. diameter (comoving distance) of the visible universe[2]
1027	1000 Ym	~250 billion light years = 2.4×1027 m = 2400 Ym	lower bound of the (possibly infinite) radius of the universe, if it is a 3-sphere, according to one estimate using the WMAP data at 95% confidence.[23] It equivalently implies that there are at minimum 21 particle horizon-sized volumes in the universe.
1028	10 000 Ym	~7.8 trillion light years = 7.4×1028 m = 74000 Ym	Lower bound of the homogeneous universe derived from the Planck spacecraft [24]
	Ym	megaparsecs = m = Ym	The size of the universe according to chaotic inflation theory.
[note 1]	Ym	megaparsecs =  m = Ym	According to the laws of probability, the distance one must travel until one encounters a volume of space identical to our observable universe with conditions identical to our own.[25][26]
[note 1]	Ym	Mpc =  m = Ym	size of universe after cosmological inflation, implied by one resolution of the No-Boundary Proposal[27]