Ask A Scientist General Science Archive

name         Rita W.
status       educator
age          60s

Question -   I have tried multiple sources to get an answer to this
but with no success.
Junior high students are interested in speed. In trying to tie Math and
Science
I am using speed. What is the orbital speed of our solar system? What is the
speed of our galaxy? Is the galaxy moving at the speed of light?
I realize these are basic questions, but not easy to find answers. No one
seems to want to bother with them. Hope you can help.
----------------
Visit this page to get some insight into orbital velocity of the planets:

http://www.windows.ucar.edu/glossary/orbital_velocity.html

(Make sure you check out the linked page.)

To calculate the orbital velocity of the earth around the sun... and get
your kids to do some math... calculate the distance the earth travels in its
orbit - pi times d - where d is twice the radius.  Many kids know the
93,000,000 mile number.  The trip around the sun is one year... 365 days
(actually 365.24) ... times 24 for hours... times 60 for minutes...  times
60 for seconds.

Ultimately you can get miles per second.  Convert to km per sec if you wish.
Math galore!

The students will be surprised when they equate the speed of the earth with
normal daily travel.

One thought... the earth's orbit is not really round, rather elliptical.
Yet it is close enough to a circle to get you a reasonable answer, and when
you ponder why the number you generate is not exactly the given, this can
enter the conversation.

Have you calculated how fast you are traveling as a result of the earth's
rotation on its axis?  It too surprises the kids.

Larry Krengel
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Dear Rita,

All speeds are rounded.
Earth's revolutionary speed - 900 mph
So just standing on the surface, watching day turn to night, we are flying by
Earth's orbital speed - 19 miles per second or about 68,400 mph
The solar system is traveling at bout 1 million miles each day as the galaxy
rotates.
Pretty quick!
Tell those kids to slow down!
Have fun

Martha Croll
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The solar system does not rotate as a unit; each planet has its own orbit
with its own period.  Earth's orbit is 93,000,000 miles in radius (584,336,234
miles in circumference) and it makes this in a year, so it is going 67,000 
miles
per hour.  I do not know about our galaxy, but it cannot be moving at anywhere
near the speed of light (relative to other galaxies) because if it were, the
light from those galaxies would be noticeably red- or blue-shifted.

--
Tim Mooney
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