'Time Machine' on Beeb 1

Just watching this currently, and the presenter has just said that our
orbit shifts every 20,000 years, 'like a pendulum'.

What the furry heck is he talking about?

Jim
--
AIM/iSight:JCAndrew2 - Log in and say 'hi'
"We deal in the moral equivalent of black holes, where the normal
laws of right and wrong break down; beyond those metaphysical
event horizons there exist ... special circumstances" - Use Of Weapons

(Jim) wrote:

Just watching this currently, and the presenter has just said that our
orbit shifts every 20,000 years, 'like a pendulum'.

What the furry heck is he talking about?

Precession of the polar axis? That's about 20,000 years IIRC. It's
more like a gyroscope than a pendulum though.


Tim
--
My last .sig was rubbish too.

Tim Auton tim.auton@uton.[groupSexWithoutTheY] wrote:

Just watching this currently, and the presenter has just said that our
orbit shifts every 20,000 years, 'like a pendulum'.

What the furry heck is he talking about?

Precession of the polar axis? That's about 20,000 years IIRC. It's
more like a gyroscope than a pendulum though.

That was my thought, but that has bugger all to do with our orbit - it's
an axial inclination thing, isn't it?

Jim
--
AIM/iSight:JCAndrew2 - Log in and say 'hi'
"We deal in the moral equivalent of black holes, where the normal
laws of right and wrong break down; beyond those metaphysical
event horizons there exist ... special circumstances" - Use Of Weapons

(Jim) wrote:

Just watching this currently, and the presenter has just said

The presenter is Jeremy Vine. Do they get more annoying than he?

A. No
B. No

Tick the correct answer.

The closest to what he might mean is the combination of equinox and
preihelion precession - 22,000 years IIRC.

--
Martin Frey
http://www.hadastro.org.uk
N 51 02 E 0 47

Martin Frey wrote:

The presenter is Jeremy Vine. Do they get more annoying than he?

A. No
B. No

'All of the above'?

The closest to what he might mean is the combination of equinox and
preihelion precession - 22,000 years IIRC.

Excuse my stupidity, but does that affect our actual *orbit* or just the
axial inclination?

Jim
--
AIM/iSight:JCAndrew2 - Log in and say 'hi'
"We deal in the moral equivalent of black holes, where the normal
laws of right and wrong break down; beyond those metaphysical
event horizons there exist ... special circumstances" - Use Of Weapons

Jim wrote
Just watching this currently, and the presenter has just said that our
orbit shifts every 20,000 years, 'like a pendulum'.

What the furry heck is he talking about?

Jim

Pick any answer below;

a. A triumph of style over content.
b. It's the BBC arty types attempt at introducing more science content
to programming.
c. It's designed to appeal to the widest audience, i.e. dumbing down.
d. Graphics are hot in cinema and TV at the moment, so if it has lots it
must be good.

Sometimes I despair for my own country and its' education.

Denis
--
DT
Replace nospam with the antithesis of hills

(Jim) wrote:
Tim Auton tim.auton@uton.[groupSexWithoutTheY] wrote:

Just watching this currently, and the presenter has just said that our
orbit shifts every 20,000 years, 'like a pendulum'.

What the furry heck is he talking about?

Precession of the polar axis? That's about 20,000 years IIRC. It's
more like a gyroscope than a pendulum though.

That was my thought, but that has bugger all to do with our orbit - it's
an axial inclination thing, isn't it?

It is indeed. I wonder if there is a similar precession of the
ecliptic? Hmmm...

[quick search]

Perhaps he was talking about perihelion precession? That cycles every
21,000 years, apparently.

http://en.wikipedia.org/wiki/Precession

http://aa.usno.navy.mil/faq/docs/seasons_orbit.html


Tim
--
My last .sig was rubbish too.

Basically its the combined effects of the moon and suns gravity on our axial
inclination (due to the rotation of a non-spherical body) plus a
contribution from the differential rotation of the Earths inner and outer
cores.

Science on the TV is written by cretins with IQ's smaller than their shoe
sizes, Don't ask about the audience.......they are all watching Big Brother.


pj


"Jim" wrote in message
...
Martin Frey wrote:

The presenter is Jeremy Vine. Do they get more annoying than he?

A. No
B. No

'All of the above'?

The closest to what he might mean is the combination of equinox and
preihelion precession - 22,000 years IIRC.

Excuse my stupidity, but does that affect our actual *orbit* or just the
axial inclination?

Jim
--
AIM/iSight:JCAndrew2 - Log in and say 'hi'
"We deal in the moral equivalent of black holes, where the normal
laws of right and wrong break down; beyond those metaphysical
event horizons there exist ... special circumstances" - Use Of Weapons

"Jim" wrote in message
. ..
Just watching this currently, and the presenter has just said that our
orbit shifts every 20,000 years, 'like a pendulum'.

What the furry heck is he talking about?

Google for "Milankovitch Cycle", the 23 kyr component
is the precession of the equinox, the 41 kyr component
is the axial tilt, and ~ 100 kyr component is eccentricity.

RonL


--
"Ignorance is the most delightful of the sciences .."

Ron Larham wrote:

What the furry heck is he talking about?

Google for "Milankovitch Cycle", the 23 kyr component
is the precession of the equinox, the 41 kyr component
is the axial tilt, and ~ 100 kyr component is eccentricity.

Thanks for that - most interesting.

Jim
--
AIM/iSight:JCAndrew2 - Log in and say 'hi'
"We deal in the moral equivalent of black holes, where the normal
laws of right and wrong break down; beyond those metaphysical
event horizons there exist ... special circumstances" - Use Of Weapons