Two questions

These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?

Question 2.
Were all planets at the same distance from the
sun 100 million years ago as they are today?

Zdenek Jizba wrote:
These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?

The Hubble parameter is about 72 km/s/Mpc, which is equal to
about 2.3 * 10^(-18) 1/s. H is the relative expansion rate,
i.e. Rdot/R. If we assumed this for the Earth, we get about
Rdot = 1.5 * 10^(-14) km/s (with R = 6380 km), i.e. in
1 million years, R would increase by about 0.47 km. Not that much...


Question 2.
Were all planets at the same distance from the
sun 100 million years ago as they are today?

I don't think so. There are various effects which could change
the orbital distances: interactions with the other planets, with
the interplanetar medium etc.

But I have no clue how big these effects are.


Bye,
Bjoern

"Zdenek Jizba" wrote in message
news:wz4fe.740$w81.359@trnddc06...
These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?


The Earth is expanding at the same rate as the Universe, because it is part
of it. The tip of your nose and all the atoms in it are also expandin g at
the same rate.

The change in 1 million years is infinitistimal. Here goes:

The Universe is probably about 30 billion light years across, and the edge
recedes at the speed of light. So each year it gets 1 light year bigger -
about on part in 30 billion. 1 million years would be one part in 30,000.
The Earth is about 15,000 kms across, so its about half a kilometer. Hmm ...
maybe not so infintistimal ... I'll think about this some more.



Question 2.
Were all planets at the same distance from the
sun 100 million years ago as they are today?

Yes.
There may at some stage have existed a Mars sized planet between Mars and
Jupiter that somehow broke to form the asteroid belt. I assume this happened
soon after the solar system was formed (if it happened at all). Otherwise
planetary orbits have been stable for billions of years.

In message , Peter Webb
writes

"Zdenek Jizba" wrote in message
news:wz4fe.740$w81.359@trnddc06...
These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?


The Earth is expanding at the same rate as the Universe, because it is part
of it. The tip of your nose and all the atoms in it are also expandin g at
the same rate.

Not according to current theory. Look at
http://www.physics.adelaide.edu.au/~...R/expanding_un
iverse.html, for instance. But AFAIK, it's not (yet ?) possible to
measure such expansion if it was occurring, either on Earth or between
the Earth and Moon.

The Universe is probably about 30 billion light years across, and the
edge
recedes at the speed of light.


No. The _observable_ universe is expanding at the speed of light, but
the current rate of expansion of the local universe is given by the
Hubble constant (70 km/s/Mpc, or whatever the current figure is) So you
have to turn that last bit (megaparsecs, 3.26 million light years) back
into kilometres to get the expansion rate of the Earth.




Question 2.
Were all planets at the same distance from the
sun 100 million years ago as they are today?

Yes.

There's no way of knowing, but some theories say not. Look at
http://www.space.com/scienceastronomy/mystery_monday_031201.html, for
instance.
It's known that there were more days in an Earth year several hundred
million years ago, but that's usually ascribed to the tidal action of
the Moon slowing the Earth. If the Earth had actually moved away from
the Sun (due to mass loss from the sun, for instance) I can't think of
any way to find out.
--
Remove spam and invalid from address to reply.

Dear Zdenek Jizba:

"Zdenek Jizba" wrote in message
news:wz4fe.740$w81.359@trnddc06...
These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?

Excellent response by Bjoern Feuerbacher.

Question 2.
Were all planets at the same distance from the
sun 100 million years ago as they are today?

The only thing I can add is that the Moon has left a pretty
continuous record in "tidal rhythmites" over the last 2 billion
years. Not that the lunar recession is entirely (or at all) due
to universal expansion. In lunar recession, angular momentum
transfer from the spinning Earth to the Earth-Moon system is the
major player. No such mechanism in Universal expansion, unless
Dark Energy is the player.

David A. Smith

N:dlzc D:aol T:com (dlzc) wrote:


The only thing I can add is that the Moon has left a pretty
continuous record in "tidal rhythmites" over the last 2 billion
years. Not that the lunar recession is entirely (or at all) due
to universal expansion. In lunar recession, angular momentum
transfer from the spinning Earth to the Earth-Moon system is the
major player.
How does it get transferred?
Lots of Greetings!
Volker

Zdenek Jizba wrote:
These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?

Question 2.
Were all planets at the same distance from the
sun 100 million years ago as they are today?

I think that the local gravitational forces overwhlem that due to the
current expansion of space and as a result there is no local expansion
effect, not now anyway. In the far far future (trillions of years from
now?) everything might get ripped apart though since the expansion
appears to be accelerating!

"Bjoern Feuerbacher" wrote in message
...
Zdenek Jizba wrote:
These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?

The Hubble parameter is about 72 km/s/Mpc, which is equal to
about 2.3 * 10^(-18) 1/s. H is the relative expansion rate,
i.e. Rdot/R. If we assumed this for the Earth, we get about
Rdot = 1.5 * 10^(-14) km/s (with R = 6380 km), i.e. in
1 million years, R would increase by about 0.47 km. Not that much...

And in 4.5 billion years it would have expanded to just under
2.4 AU. That's larger than the radius of Mar's orbit, which is
about 1.5 AU. Since by a variety of dating techniques the Earth
is at least 4.5 billion years old, this would seem to be pretty
convincing evidence that common objects like planets do not
participate directly in the expansion of the universe.

"Peter Webb" wrote in message
u...

"Zdenek Jizba" wrote in message
news:wz4fe.740$w81.359@trnddc06...
These questions are strictly hypothetical.

Question 1.
If the earth expanded at the same rate as the
universe, how much would the radius increase in 1
million years?


The Earth is expanding at the same rate as the Universe, because it is
part of it. The tip of your nose and all the atoms in it are also expandin
g at the same rate.

Dead wrong.

Dear Volker Hetzer:

"Volker Hetzer" wrote in message
...
N:dlzc D:aol T:com (dlzc) wrote:


The only thing I can add is that the Moon
has left a pretty continuous record in
"tidal rhythmites" over the last 2 billion years. Not that
the lunar recession is
entirely (or at all) due to universal
expansion. In lunar recession, angular
momentum transfer from the spinning
Earth to the Earth-Moon system is the major player.

How does it get transferred?

Pour a little coffee (or tea, or beer) in a cup. Swirl it
around, without using a spoon. How did you transfer angular
momentum to the fluid? You moved the container (hopefully).
Like a miner panning for gold.

The water on the Earth is like a "moving container", in that its
(the water's) contribution to spacetime (sorry Bjoern) is always
a little ahead of the Earth. The water sloshes momentum onto the
Moon, and brakes the Earth with tidal friction. In periods
"known" for high glaciation, the recorded lunar recession rate
was low.

To repair any damage I probably did:
Google Advanced
all the words: Earth Moon
exact phrase: angular momentum
either word: tide tidal
from domains: .edu
only 610 hits, like:
URL:http://csep10.phys.utk.edu/astr161/lect/moon/tidal.html
URL:http://burro.cwru.edu/Academics/Astr...earthmoon.html
URL:http://www.sunspot.noao.edu/sunspot/...ok/expl-6.html

Lots of Greetings!

To you as well.

David A. Smith