# The Naked Scientists Forum

### Author Topic: Is the earth flat?  (Read 5028 times)

#### Villi

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##### Is the earth flat?
« on: 26/06/2016 06:46:45 »
Most of my limited knowledge from school, media and what everyone says suggests the earth is round. However, I've come across a lot of recent stuff that's tickling my brain and I'm wondering if the earth is flat. What are some experiments I can do to disprove the earth is flat theory?

For example, they say we are in a dome, the sun is a couple thousand miles up and going in a circle above the flat earth map. I'm guessing I need a telescope? I honestly don't feel like spending money or time on this though. Just wondering about what people think.

#### Colin2B

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##### Re: Is the earth flat?
« Reply #1 on: 26/06/2016 09:00:51 »
This comes up with some regularity as the flat earthers go to very convoluted lengths to provide arguments to 'prove' their case.
Usually we move such discussion to new theories or more properly 'it can't be true'.

Some experiments you can do:

Use a telescope to watch a ship going over the horizon, you will see the bottom part disappears first, superstructure last so the surface of earth is curved.

The curvature can be measured. Put 3 posts in a lake as far apart as possible, so they stick up the same amount above the water, then sight across the tops. You will see the centre post is higher because of the curvature. You can measure this curvature all over the earth and it is roughly the same.

Look at the pole star and measure its elevation (angle to ground). This matches your latitude on a map. If you try to draw out the geometry for the elevation at different latitudes and assume a flat earth it doesn't work, has to be a sphere.

You can do the same with their claim that the sun is only a few thousand miles up, it doesn't work out.

Look at the moon, it's a sphere. No reason to believe earth is not the same.

PS this topic is likely to be moved.

#### alancalverd

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##### Re: Is the earth flat?
« Reply #2 on: 26/06/2016 09:31:12 »
No need to do any experiments for yourself. Aristarchus and Eratosthenes provided a heliocentric model and measured the diameter of the spherical earth, about 2500 years ago. Their work is widely published in elementary schoolbooks.

If you think things might have changed recently, talk to any surveyor, cartographer, soldier, sailor, pilot or astronaut, and ask them how they get from A to B without using spherical geometry. (The rest of us use numbered roads, so generally have no idea!)

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#### hamdani yusuf

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##### Re: Is the earth flat?
« Reply #3 on: 26/06/2016 11:25:02 »
http://www.popsci.com/10-ways-you-can-prove-earth-is-round#
For point #8 in the list, you can prove it yourself easily if you have someone you know on different longitude. You can chat or even make a video call with them and ask them what time is it now.
I'd like to add one more thing to the list. If you are on Northern hemisphere, you will see stars move counterclockwise in circular trajectory around polaris. But if you are on Southern hemisphere, you will see stars move clockwise. This is impossible if only the earth was flat.

#### jeffreyH

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##### Re: Is the earth flat?
« Reply #4 on: 27/06/2016 02:02:19 »
Or you could watch videos made on the ISS and see the earth rotate. There are so many ways to prove the point. I often wonder if the idea of believers in a flat earth in the past was not just a relatively recent urban myth to make our modern day selves feel superior.

#### jeffreyH

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##### Re: Is the earth flat?
« Reply #5 on: 27/06/2016 02:27:52 »

#### hamdani yusuf

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##### Re: Is the earth flat?
« Reply #6 on: 27/06/2016 02:50:11 »
Or you could watch videos made on the ISS and see the earth rotate. There are so many ways to prove the point. I often wonder if the idea of believers in a flat earth in the past was not just a relatively recent urban myth to make our modern day selves feel superior.
Flat earthers reject videos by saying that videos are not real and can be easily manipulated.

#### Villi

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##### Re: Is the earth flat?
« Reply #7 on: 27/06/2016 08:15:24 »
Apologies if this topic is in the wrong forum. Move as necessary.

So it seems the telescope thing is most accessible to me.

I did some math and for a ship to disappear under 100m of curvature of the 6371km radius earth, it would have to travel 36km. Someone please verify this because math is one of my weakest subjects.

Now I just need to find the right telescope and a way to track a ships movement/distance.

To be clear, I still think the earth is round, but I really want to do something with my own hands to prove it.

#### alancalverd

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##### Re: Is the earth flat?
« Reply #8 on: 27/06/2016 10:03:57 »
No need for a telescope. Use http://www.ringbell.co.uk/info/hdist.htm to calculate the horizon distance from a given observer height above sea level, then stand on the beach and watch a small boat.

From 2 meters above sea level, the horizon is about 5.1 km, well within unaided visual range on a clear day.

Or try walking along a very long concave curved beach (the Jurassic Coast is excellent, as is Morecambe Bay and several sandy bays in Scotland. At some point you won't be able to see the far end of the beach. Take a friend or child, significantly taller or shorter than yourself, and ask them when the landmark disappears. If the earth were flat, it wouldn't disappear at all, or would disappear at the same distance for both of you if you believe the worst poppycock.

Or try climbing the cliff at  one end of the long beach - can you see further than at sea level? Try sitting down - is the horizon closer?

You can compare your measurements with the horizon calculator, which is based on a simple spherical model, or use the tables in Reed's Nautical Almanac (based on a 2 m asl observation point for yachtsmen) or the AOPA Pilot's Manual (if you are very tall!)

#### Colin2B

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##### Re: Is the earth flat?
« Reply #9 on: 27/06/2016 10:45:17 »
The only thing I would add to what Alan said is that if you are looking at ships it's worth being high enough to avoid wave height confusing the exact point of disappearance.

You might find the following table useful as well as the ref Alan gave (Reed's costs money). http://www.sailtrain.co.uk/navigation/rising.htm

If the subject really interests you a text on astro navigation will be quite enlightening along with some basic astronomy. There is a lot on the web.

#### PmbPhy

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##### Re: Is the earth flat?
« Reply #10 on: 27/06/2016 14:58:26 »
Quote from: Villi
For example, they say we are in a dome, the sun is a couple thousand miles up and going in a circle above the flat earth map. I'm guessing I need a telescope? I honestly don't feel like spending money or time on this though. Just wondering about what people think.
If that were true then the Sun would never set, and yet it does. If that were true then ships on the ocean would never disappear below the horizon, and yet they do. If that were true then the set of stars people in the northern hemisphere would be the same set of stars as the people in the southern hemisphere would see, and yet they aren't. If that were true then distance measurements between locations on the earth would tell us that the earth was flat, and yet they don't. They tell us that the earth is a sphere.

Etc, etc, etc.

#### Alan McDougall

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##### Re: Is the earth flat?
« Reply #11 on: 27/06/2016 22:02:17 »
If the Earth were flat, gravity would work in some very weird unknown way.

To answer you question no the Earth in not flat is a roundish Object held in the gravity field of Its star namely our beautiful golden sun that rises in the east and sets in the west precisely because the Earth is round and revolving on its axis!

Alan

#### Colin2B

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##### Re: Is the earth flat?
« Reply #12 on: 27/06/2016 23:22:04 »
If the Earth were flat, gravity would work in some very weird unknown way.
Actually it's not unknown, but is calculatable. I was thinking of putting the question up.
On a spherical earth the downward pull towards the centre is the resultant of the sum of all the vectors from the distributed mass. That means there is a significant, but small, sideways pull which balances out.
If the earth were flat you would get a much greater sideways pull if you were at the centre of the disc, would that make us wider than we are?? Towards the edge of the disc, the pull would become asymmetric pulling you back towards the centre of the disc. I haven't got the time to do the calculations, anyone fancy a go?

#### PmbPhy

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##### Re: Is the earth flat?
« Reply #13 on: 28/06/2016 04:43:18 »
If the Earth were flat, gravity would work in some very weird unknown way.
Actually it's not unknown, but is calculatable. I was thinking of putting the question up.
On a spherical earth the downward pull towards the centre is the resultant of the sum of all the vectors from the distributed mass. That means there is a significant, but small, sideways pull which balances out.
If the earth were flat you would get a much greater sideways pull if you were at the centre of the disc, would that make us wider than we are?? Towards the edge of the disc, the pull would become asymmetric pulling you back towards the centre of the disc. I haven't got the time to do the calculations, anyone fancy a go?

Let's not forget that if the Earth was flat as they claim it is then the sun would fall down and all the geostationary satellites that are orbiting the earth wouldn't be there. So much for DirectTV, huh? Lol!

#### Alan McDougall

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##### Re: Is the earth flat?
« Reply #14 on: 28/06/2016 05:23:48 »
Look at Terry Pratchets Flat Earth/World

#### Villi

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##### Re: Is the earth flat?
« Reply #15 on: 01/07/2016 05:47:38 »
That site verified my math is correct, although it was in reverse and I put in 100m to cover any possible cruise ship. Thanks.

I really need a telescope because I'm very near-sighted. Things may as well not exist beyond a hundred metres for me.

I also don't know squat about astronomy and can't readily view stars from the city I'm in. Nor do I know what light and photons are, so I can't explain why I see the things I do. I know the sun sets and rises east to west. The flat earthers have some interesting ideas and probably unconfirmed facts about all this. That light doesn't go forever and that it bends. The sun goes in a circle in one direction east to west for us. No one's gotten past Antarctica. That what we see as the moon, stars and other planets are holograms on the dome or something. That anything NASA says or gives data about it probes and missions is false. We don't know what gravity is and we are only starting to detect gravitational waves.

I've personally never confirmed anything I was taught about in physics to astronomy. I've only ever flown in planes and have not seen curvature (but I wasn't looking for it) nor have I gone in space to see earth orbiting the sun. Basically all I'm saying is I don't know anything. I at least want to see a boat disappear under the horizon.

#### YarS

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##### Re: Is the earth flat?
« Reply #16 on: 01/07/2016 21:06:15 »
From 2 meters above sea level, the horizon is about 5.1 km, well within unaided visual range on a clear day.
Formally, it can be a result of somekind of atmospheric refraction.

#### YarS

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##### Re: Is the earth flat?
« Reply #17 on: 01/07/2016 21:14:31 »
Or you could watch videos made on the ISS and see the earth rotate. There are so many ways to prove the point. I often wonder if the idea of believers in a flat earth in the past was not just a relatively recent urban myth to make our modern day selves feel superior.
Coin is flat, but spinning coin looks like a sphere.

#### Colin2B

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##### Re: Is the earth flat?
« Reply #18 on: 02/07/2016 08:43:58 »
Formally, it can be a result of somekind of atmospheric refraction.
Refraction moves the apparent position of an object complete with its horizon, it does not produce an obscuring effect. Try tracing out the ray diagrams.

Coin is flat, but spinning coin looks like a sphere.
Spinning at that speed, the stars would appear to be a blur.

If you have an alternative theory to the spherical earth please post it in New Theories or It Can't Be True. See http://www.thenakedscientists.com/forum/index.php?topic=66954.0

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#### Villi

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##### Re: Is the earth flat?
« Reply #19 on: 07/07/2016 06:03:52 »
I ordered a very inexpensive telescope.

360/50mm. Can anyone explain to me what this means? I'm assuming it's sufficient to view past a few 100km since these things look at stuff in space.

Is it dangerous to use these things in daylight? I recall reading that looking at the sun with a telescope destroys your eye.

#### YarS

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##### Re: Is the earth flat?
« Reply #20 on: 07/07/2016 07:29:41 »
Formally, it can be a result of somekind of atmospheric refraction.
Refraction moves the apparent position of an object complete with its horizon, it does not produce an obscuring effect.
Usually - yes. But there are such thing as "negative refraction".

Quote
Spinning at that speed, the stars would appear to be a blur.
May be, may be not. May be celestial sphere with stars are moving too.

Quote
If you have an alternative theory to the spherical earth please post it in New Theories or It Can't Be True. See http://www.thenakedscientists.com/forum/index.php?topic=66954.0
I have no alternative theory, of course. I just wanna say, that there are no such thing as "proof" in natural science. And topicstarter can't "disproof" model of "flat Earth", becouse there are no any working models of it.

#### PmbPhy

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##### Re: Is the earth flat?
« Reply #21 on: 10/07/2016 06:30:02 »
One of the most obvious reasons that we know that the Earth is not flat is because artificial satellites could not stay above a flat Earth. They'd fall down. However they can easily orbit the spherical Earth.

#### syhprum

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##### Re: Is the earth flat?
« Reply #22 on: 10/07/2016 06:48:24 »
The best evidence that the world is flat is the way projectiles move under the influence of gravity, it is widely reported that they move in a parabolic path which only happens because the world is flat and of infinite extent.
if the earth was spherical they would take an elliptical path

#### alancalverd

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##### Re: Is the earth flat?
« Reply #23 on: 10/07/2016 10:01:29 »
Everyone gets a prize.

The earth is flat enough for those who want it to be, and adequately spherical for those of us who need it so.

#### syhprum

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##### Re: Is the earth flat?
« Reply #24 on: 10/07/2016 11:30:23 »
I would like someone skilled in math's to work out what the difference in range would be for a large gun such as was developed in WWII with a range of say 45 miles if the landing point was calculated using either parabolic or elliptical parameters.

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##### Re: Is the earth flat?
« Reply #24 on: 10/07/2016 11:30:23 »