The Science Trivia Quiz

daveirl · 28-02-2003 8:15pm

This post has been deleted.

Victor · 01-03-2003 2:23pm

Originally posted by DeVore
DeV 3 : True or False: Black holes cannot be observed on Earth because nothing, not even light, can escape their event horizon...

While not observed directly, can't the effects on other bodies be detected?

bonkey · 01-03-2003 7:25pm

Originally posted by Victor
While not observed directly, can't the effects on other bodies be detected?

Most definitely.

Where the confusion comes in is that most people confuse the black hole with the singularity at the centre of a black hole.

The black hole is everything up to and including the event horizon...which eimts Hawking radiation. The singularity at the centre, however, cannot be directly detected.

As a followup trivia question :

"Nature abhors a naked singularity"

Who said it, to whom, what was it amended to "in admitting defeat" and why.

And again...no googling please. Any moron can cut and paste the quote into a search engine to find the answer.

jc

Sev · 02-03-2003 1:52pm

Originally posted by DeVore

Assumptions:
1. The earth is circular or at least uniformly oval around the axis you are drilling.

2. Its uniformly dense or (again) its variations are uniform through the length of the axis you are drilling on.

3. Air resistance is not ignored.

4. The earth isn't rotating

DeVore · 02-03-2003 2:20pm

Originally posted by Victor
While not observed directly, can't the effects on other bodies be detected?

You could say that NOTHING can be observed directly, only the light that bounces off them ... At this point you get to where Maths/Physics and Philosophy collide.
Most people accept that if you can observe an effect localised to an object you can refer to it as observation. Theres a nights drinking round a warm fire in that one though!

DeV.

DeVore · 02-03-2003 2:26pm

Originally posted by Sev
4. The earth isn't rotating

I'm wondering if it would matter if the Earth was rotating aound the shaft we've supposedly dug through it.... ?

In fact, I'm not sure that the rotation of the the earth matters. Consider that it doesnt matter when you are playing pool, or throwing a baseball... relativity comes into play I think so I dont think we require the earth not to be rotating.
(by Relativity you could equally say the earth IS stationary and the entire universe is rotating around IT, neh?)

DeV.

Sev · 02-03-2003 5:03pm

Well, the fact is.. if the earth is rotating, and youre on the surface of the earth, and you drop something towards the center, that ball that you drop has an initial velocity relative to the gravitation centre of the earth (since youre standing on an earth that is rotating), and as the ball gets closer to it, it's potential energy is converted into kinetic energy, meaning if there were no shaft constraining its decent it would begin to orbit faster and faster around that centre of gravity of the planet, where as the planet would be rotating at its constant speed. So its gonna be bumping off sides of the shaft a good few times on the way down, and lose some energy.. nothing major tho.

Sev · 02-03-2003 5:53pm

Originally posted by DeVore
(by Relativity you could equally say the earth IS stationary and the entire universe is rotating around IT, neh?)

The way I see it.. you cant mix rotation with relativity, and if you were to do that, youre turning the rest of physics upside down. Otherwise you would have to assume, for such a scenario to work, the Earth being stationary and rest of the universe kept in a tidy 24hr orbit around it, that the Earth is exhibiting some sort of massive centripetal attractive force, which is just silly

If you were to continue with this line of thinking however, and ignore such a force, and say that everything revolves around the earth anyway, cos thats just how the universe works.. then that is to say that the natural state, for any stationary element (devoid of energy) in that universe, is in that 24 hour cyclic motion around the Earth.

Therefore, if a body is stationary, in relation to this moving model of the universe, it effectively has a relative velocity, and kinetic energy relative to the earth.. and that just brings us back to the static universe model again. I hope youre following me.

Bottom line.. no it doesnt work that way.

silverside · 02-03-2003 9:19pm

but the earth's rotation *can* be observed in everyday life. Did you not see that episode of the simpsons where bart rings australia to confirm that the water in the bath spins the opposite way down there.

It's called the coriolis effect; sailors and artillerymen have to be aware of it as well.

bonkey · 02-03-2003 9:53pm

Originally posted by Sev
The way I see it.. you cant mix rotation with relativity,

Course you can

and if you were to do that, youre turning the rest of physics upside down.

But thats exactly what relativity predicts should happen.

If you change your point of reference, then you can still model a valid system. The models will not be identical, but you would be able to map one to the other.

jc

Sev · 02-03-2003 11:17pm

Originally posted by bonkey
Course you can
But thats exactly what relativity predicts should happen.

If you change your point of reference, then you can still model a valid system. The models will not be identical, but you would be able to map one to the other.

jc

I understand, that is the point I made in that third paragraph. You can change your point of reference (have the universe rotating around Earth, such that the ball youre dropping through the earth effectively appears stationary), but the ball still has a relative velocity, a relative kinetic energy in respect to the planet.
Hence, the ball is gonna hit the sides a few times on the way down towards the center of the Earth and out again, as I said, and imagining a relative situation in which the Earth isnt rotating will not change that.

But to model a similar situation where there is no initial relative velocity between the planet and the ball, you would have to assume that the earth is causing a massive centripetal force to keep the rest of the universe in its orbit.

It all makes perfect sense.

As for the coriolis effect.. yes silverside, your right, the effects of the earth's rotation can be observed, and it makes sense. I dont know why thats relevant, I never said it couldnt. However dont believe everything you see on TV. Much like the force of gravity, the coriolis effect is a very weak force indeed and only has a noticeable effect over a very large scale, for example in weather systems (why storms rotate in different directions in different hemispheres).

But to think you can detect the coriolis effect in your kitchen sink is ludicrous. Try it yourself, empty a few sinks around your house and the direction of rotation is either completely random or governed by the contours of the bowl. The toilets flush thing on the simpsons is nonsense.

Sev · 03-03-2003 5:50pm

But as my good friend Cormacadam pointed out, you could drill the shaft from the north pole to the south pole, and that would avoid the problem of the rotation of the earth.

Congoose · 04-03-2003 12:33pm

A quick one, but it took me a while to get it:

Q. Without googling, can you name the seven base S.I. units which are combined to form all the other units?

Hobart · 04-03-2003 12:40pm

kilogram (kg)
second (s)
kelvin (k)
amphere (a)
meter (m)

could never get the other 2

bonkey · 04-03-2003 12:59pm

Originally posted by Hobart
kilogram (kg)

This one always surprises me, because surely gram (g) would be the "base" unit there, not kg...but I seem to recall that you're correct here.

Cant remember the other two either. Candels are possibly one (luminosity), but I havent a clue of the other.

jc

Hobart · 04-03-2003 1:08pm

Bang on with candels. No idea either about the (kg) v gram. As soon as no 7 is posted I will google and find out why. Maybe it's something to do with the initial formation. i.e. Did the kg come before the g? Sounds silly but I seem to remember some explantion like that!

Thanx 4 The Fish · 04-03-2003 1:15pm

mole (mol) is the amount of substance.

Cannot remember why that kg v g thing is, must look it up again.

Sev · 04-03-2003 7:22pm

Here's just something I just thought of now.. by how much, every century, does our calender date, vary from the true astronomical one?

daveirl · 04-03-2003 9:35pm

This post has been deleted.

Hobart · 05-03-2003 12:28pm

Originally posted by daveirl
Just nitpicking but technically you'd be wrong using a small k for Kelvin.

The unit is named after a person so it takes a capital letter. Same applied to Ampére.

Candela (cd) is the unit of luminocity. And mole is the other one.

What is the official spelling of meter? metre or meter.

I always use metre, presumed it was the correct (i.e. Non US way)

Just nictpicking back but I think your wrong. In terms of convention the following should be observed. And I quote:

9.1 Capitalization
When spelled out in full, unit names are treated like ordinary English nouns. Thus the names of all units start with a lower-case letter, except at the beginning of a sentence.

Meter or Metre does not matter. Meter is used mostly in the states and metre is the correct UK English spelling.

Hobart · 05-03-2003 12:36pm

Couple of quick questions:

1) What is the smallest prime number?

2) What is the smallest perfect number?

Remember no googling or the questions are useless.

Sev · 05-03-2003 2:22pm

2,6

Sev · 05-03-2003 2:27pm

Well, K is most definitely used for kelvin, as opposed to k, which usually signifies a random constant, or a prefix that increases something x10^3. And A is definitely the symbol for Ampere, 'a' is often used to represent acceleration. Of course most of these letters have many other meanings too in different fields.. there arent enough letters in the alphabet

Hobart · 05-03-2003 4:00pm

Originally posted by Sev
2,6

Yes, Yes.

Congoose · 05-03-2003 6:59pm

A short follow up:

Q. In addition to the 7 base units, there are two supplementary S. I. units which are technically dimensionless, but are expressed as units anyway. What are they?

Woden · 05-03-2003 11:53pm

radian and steradian?

also yes it is K not k

Hobart · 06-03-2003 12:35am

My apologies. Indeed you are correct. The Correct abbrevation for kelvin is K and for ampere is A (both capitals).

Back to my previous questions.

Prime numbers and Perfect Numbers. It is accepted that 2 is the lowest prime number and that 6 is the smallest perfect number. But. As the number 1 'fits' the rule for both why is 1 not the lowest prime number and the smallest perfect number?

And secondly can a prime be a negative?

Remember no googling or the question is useless.

Congoose · 06-03-2003 11:02am

Originally posted by Dataisgod
radian and steradian?

Correct!

bonkey · 06-03-2003 4:08pm

Originally posted by Hobart
why is 1 not the lowest prime number and the smallest perfect number?

Technically, a prime is a number which has 2 divisors - itself and 1. 1 does not have 2 divisors, it only has one.

I'd imagine its a similar technicality for perfect's

And secondly can a prime be a negative?

Absolutely not. Every negative integer is divisible by 1, -1, and itself which means that it would have at least three divisors.

jc

Victor · 06-03-2003 8:17pm

Originally posted by bonkey
Absolutely not. Every negative integer is divisible by 1, -1, and itself which means that it would have at least three divisors.

What about -1 it is only divisable by 1 and -1?

The Science Trivia Quiz

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