Earth's Orbit around the Sun

who_ru

Hi,

i was watching a Time Team programme recently on catastrophes that have occurred on Earth. Volcanic eruptions, asteroid strikes, etc...you get the picture.

However, Tony Robinson, also identified the Ice age as a catastrophe...well yes it was you say so what's unusual about that?

well it was his explanation of it that i found interesting. Robinson's theory is that the Ice Age was caused by the Earth drifting further away from the Sun than normally, thus causing the avg temperature to drop significantly and resulting in ice sheets spreading from the poles, in the case of Europe, he reckons half the continent was covered in Ice sheets, the rest a cold desert without vegetation and nothing to sustain life on a large scale.

my question is - what could have caused the Earth's orbit to pull away from the sun so much causing the Ice age? would it not have to be the gravitational pull of another planet or star? Or was it that the Sun, for whatever reason, exerted less gravitational pull on the Earth?

He also said the the earth is drifting further away from the Sun in general, and that it is a certainty that the Ice age will return under those circumstances.

I have to say that it struck me just how much we as a species depend on near perfect conditions in order to survive, not too hot, not too cold. But the programme was at pains to explain that all of the conditions that caused previous catastrophes and the death of 99% of all species that have ever lived, are still just as threatening today as they were when they wiped out the dinosaurs etc.

At the end good old Tony finished by saying, ' it's not that we as a species have been lucky ( to survive this far), it's just that we haven't been unlucky....Yet!'

smcgiff

There will of course be yet another ice age, but the timescales involved mean it's nothing you have to worry about. Asteroids on the other hand :pac:

Captain Chaos

The Earth's orbit around the sun is not that simple at all, very complex in fact.

https://www.youtube.com/watch?v=IhqzW97_47w

Zubeneschamali

Just to be clear, the Earth's orbit is not getting further from the sun.

The changes which are thought to cause ice ages are related to the fact that the Earth's orbit is not quite circular, the ellipse moves around the Sun, the Earth's tilt is not constant, and it precesses like a gyroscope.

All of these are periodic, and the cycles add up into what are called the Milankovitch cycles.

Capt'n Midnight

smcgiff wrote: »

There will of course be yet another ice age, but the timescales involved mean it's nothing you have to worry about.

Green house gas levels mean WE have pushed back an ice age for then next 250,000 year give or take

Rubecula

Capt'n Midnight wrote: »

Green house gas levels mean WE have pushed back an ice age for then next 250,000 year give or take

Keep the climate warm, fart a lot??

Apparently methane from cattle is not the big warmer of the climate that is rumoured.

Methane from termites on the other hand.

However another ice age is pretty certain to occur at some time.

Capt'n Midnight

Rubecula wrote: »

However another ice age is pretty certain to occur at some time.

yeah it's fairly likely

But look at Venus.


Having the earth become so hot that its uninhabibatible is a certainty. Because the sun will expand.

Rubecula

I have often thought that if we could seed Venus with extremophiles to fix the carbon and thereby releasing oxygen, the place could become habitable.

Take a while though, a few thousand years at the minimum.

Still the sun is not going to be getting bigger for about 5 billion years it seems.

Capt'n Midnight

Rubecula wrote: »

I have often thought that if we could seed Venus with extremophiles to fix the carbon and thereby releasing oxygen, the place could become habitable.

thought they had ruled out that as not feasible or that you'd need more hydrogen ?

slade_x

Capt'n Midnight wrote: »

thought they had ruled out that as not feasible or that you'd need more hydrogen ?

Yes, the challenge involved would be a far too costly and not to mention completely outside the realm of our current capabilities. Sure enough you could get the oxygen from the carbon dioxide in the atmosphere but you'd be extremely short on hydrogen to form water to combine with the remaining co2 for photosynthesis and you'd also have a hard time trying to get sunlight for that reaction on the surface too. to make matters worse on the surface the atmospheric pressure as you probably already know, to round up are almost 100 times more than that of earths at sea level and temperatures reaching almost 500 degrees celsius, at those temperatures and pressure's co2 neither resembles its gaseous phase nor even a distinct liquid phase

On the bright side though at about 30 miles above the surface temperatures and pressures do become more earth like also the following subheading entitled possibilty of life from wikipedia may be of interest:

http://en.wikipedia.org/wiki/Atmosphere_of_Venus#Possibility_of_life

Rubecula

If there was someway to lower the temperature on Venus, the other problems could be overcome in time. and we have a fair bit of that.

But hot acid rain is not easy to overcome. The pressure could be suited up against, the acid rain could be protected against. It is just that combined with the heat it is a bigger problem.

That is why I though extremeophiles could aid in terraforming.

Venus should be generous and give a load of atmosphere and heat to Mars. That would give us two other planets to colonise given a bit of time.

Expensive? Only if it is all done in one hit. Spread out over a thousand years or so it would not be that expensive surely?

Batsy

The Earth's axis of rotation is currently tilted at 23.5 degrees from vertical in relation to the orbital plane around the Sun. This tilt changes. It ranges from 22 degrees to 25 degrees. It takes about 41,000 years to make one cycle. When the tilt is 25 degrees the poles get more sun and are warmer than the equator. When the tilt is 22 degrees the poles are colder and it is warmer at the equator.

http://books.google.co.uk/books?id=8MgCR50FP8kC&pg=PA34&lpg=PA34&dq=ice+ages+earth's+processional+tilt&source=bl&ots=ih9k9CCKFx&sig=z9N9IyIDAVkjLtTvFtHGfbhANqk&hl=en&sa=X&ei=WVRBT_uhIOSg0QX3rvyODw&ved=0CCgQ6AEwAQ#v=onepage&q&f=false

Cú Giobach

Batsy wrote: »

The Earth's axis of rotation is currently tilted at 23.5 degrees from vertical in relation to the orbital plane around the Sun. This tilt changes. It ranges from 22 degrees to 25 degrees. It takes about 41,000 years to make one cycle. When the tilt is 25 degrees the poles get more sun and are warmer than the equator. When the tilt is 22 degrees the poles are colder and it is warmer at the equator.

http://books.google.co.uk/books?id=8MgCR50FP8kC&pg=PA34&lpg=PA34&dq=ice+ages+earth's+processional+tilt&source=bl&ots=ih9k9CCKFx&sig=z9N9IyIDAVkjLtTvFtHGfbhANqk&hl=en&sa=X&ei=WVRBT_uhIOSg0QX3rvyODw&ved=0CCgQ6AEwAQ#v=onepage&q&f=false

I think you misread that page, it says the poles would be warmer, not warmer than the equator.
An 3 deg increase in tilt (from 22 deg) makes seasons more extreme, moves the lines of the tropics and the antarctic or arctic circles 3degs north or south. (The Arctic circle would move about 200 miles south, the tropic of Cancer about 200 miles North).
The Sun at the poles would be 3deg higher in summer but 3deg lower in winter, giving a "deeper" winter as well as a warmer summer.
The Sun would still be directly overhead at the Equator at the equinoxes as it is now.
A 3 deg difference in the hight of the Sun is about the difference in hight between the midday Sun viewed from Cork or viewed from Derry.