Heavy Earth
 Q:
The earth gets heavier each day with the meteors and space debris that lands.
Does Earth ever lose weight? If not, wouldn't Earth eventually get so heavy so
as to affect its orbit?
A: Earth does indeed
get heavier with landing space debris--several tons of dust and micrometeorites,
alone, hit Earth's atmosphere each day. When you include the big rocks that
actually impact Earth, this debris adds up to 40,000 metric tons a year.
Figure: [NOAA] The
launch of TIROS I, the birth of the meteorological satellite system in 1960.
Does Earth throw off weight at anything like this rate, you
ask. The two ways Earth might are: hot atmospheric molecules escaping Earth's
gravity or launched space vehicles. I asked the National Oceanic and Atmospheric
Administration (NOAA) how much atmosphere do we lose each year.
"I do not have definitive information... but [outgoing
material] is so insignificant relative to the mass of the Earth that the ratio
would be a decimal followed by all the 0's you could put on this page," says
Russ Schnell, Director of the NOAA Observatory Operations in charge of
collecting atmospheric data.
That leaves space programs. About 5,000 satellites have been
launched since Sputnik 1 took off in 1957. Suppose all those satellites were
still in space and as large as 3.5-metric tons (a larger than average
satellite).
Then all the satellites the world has ever launched would
total 17,500 metric tons of mass--which is only about 0.000000001 of one percent
of the meteor mass that has landed on Earth. The number of zeros following the
decimal place doesn't fill a page but it's still a pretty small number.
We can, therefore, forget about Earth bailing out mass. She
doesn't, at least not compared to what lands on her.
Now the question remains. Over the eons, has Earth picked up
enough mass from falling space debris to affect her orbit? This mass adds up to
about ten raised to the 14th power metric tons, assuming Earth has
always added weight at the present rate of 40,000 metric tons per year. That
total seems like a lot until you compare it to the immense size of Earth. Then
it dwindles to a pathetic 0.000003 of one percent of the mass of Earth.
Negligible.
Accumulating space debris over the years has not affected
Earth's orbit around the Sun one whit.
Further Surfing:
Cornell U, Ask a Scientist
Cosmic and
heliospheric learning center |
