Astronomy and Space

[Grumble]

Not strictly astronomy, but is there such a thing as a globe that illuminates half the surface to allow you to show how the seasons work? I’m imagining a tilted globe but with the light terminator being vertical, so that when you spin it, it simulates the day light at a particular time of year. You would have to be able to move the light around to change the time of year.

[Gfamily]

Not strictly astronomy, but is there such a thing as a globe that illuminates half the surface to allow you to show how the seasons work? I’m imagining a tilted globe but with the light terminator being vertical, so that when you spin it, it simulates the day light at a particular time of year. You would have to be able to move the light around to change the time of year.

If this is for teaching purposes, we used a globe bulb on a table lamp without a lampshade to stand for the Sun, and then gave a polystyrene ball on a stick (held at an angle towards one wall) to each person, that they could walk around the table lamp to show how the sunlight fell more on one hemisphere then the other.

[Grumble]

Not strictly astronomy, but is there such a thing as a globe that illuminates half the surface to allow you to show how the seasons work? I’m imagining a tilted globe but with the light terminator being vertical, so that when you spin it, it simulates the day light at a particular time of year. You would have to be able to move the light around to change the time of year.

If this is for teaching purposes, we used a globe bulb on a table lamp without a lampshade to stand for the Sun, and then gave a polystyrene ball on a stick (held at an angle towards one wall) to each person, that they could walk around the table lamp to show how the sunlight fell more on one hemisphere then the other.

I know how to do that, it’s just in my house that I’m thinking. We have a light up globe, I just thought it would be cool to make it work differently. With modern LEDs I’m sure you could make it happen.

[IvanV]

Not strictly astronomy, but is there such a thing as a globe that illuminates half the surface to allow you to show how the seasons work? I’m imagining a tilted globe but with the light terminator being vertical, so that when you spin it, it simulates the day light at a particular time of year. You would have to be able to move the light around to change the time of year.

If this is for teaching purposes, we used a globe bulb on a table lamp without a lampshade to stand for the Sun, and then gave a polystyrene ball on a stick (held at an angle towards one wall) to each person, that they could walk around the table lamp to show how the sunlight fell more on one hemisphere then the other.

I know how to do that, it’s just in my house that I’m thinking. We have a light up globe, I just thought it would be cool to make it work differently. With modern LEDs I’m sure you could make it happen.

You could actually buy one, a little while ago, but it has been discontinued. It was the Elenco Night & Day Globe. It seems to be not very easy, which is why this is the only model I have found, even in specialist globe retailers, and it has been discontinued. But you can look at this manual and perhaps gain some clues from the mechanism it depicts.

With a globe that is lit externally, you would need the light to be at some distance from the globe to present a sharp day/night terminator. The light could remain in a fixed location, but you'd have to generate the seasons by rotating the globe base so that the axis rotated relative to the light.

With a globe that lights up in the interior, what you'd really need would be an internal light-proof vertical partition, with a light on one side of it, to separate day and night. But as it would turn on a different axis from the external globe's axis, that would be bit tricky to arrange. Maybe there'd be some trick with something that looks a bit like the mechanism of a maritime self-levelling compass, but with pivots at an angle of 23 degrees rather than 90 degrees, you'd have in the interior to organise it. Or maybe you'd some kind of a channel around the antarctic circle, as some point of the antarctic circle would always be at the lowest point, that the axis would pierce through. Though if you can rotate something all the way around the antarctic circle, how does the globe avoid falling into two pieces. In fact, having a look at that Elenco globe manual, basically they don't have anything south of the antarctic circle. They rotate the upper part of the globe around the blank antarctic circle piece. There is a partition inside the globe with a bright light on one side of it. The partition rotates around a vertical axis that is fixed to one edge of this fixed antarctic circle part.

It strikes me that you could alternatively have an external hemisphere, which covers over the night side, to separate them. But it would need some kind of provision that the fixing for the globe's own axis could move through it, when the south pole was in antarctic summer, for example. So that would also be awkward, but again maybe something that looks a bit like a self-levelling compass would achieve it.

You could in principle stud the globe with lots of little LEDs, but you'd need a computer program to select them.

[Grumble]

If this is for teaching purposes, we used a globe bulb on a table lamp without a lampshade to stand for the Sun, and then gave a polystyrene ball on a stick (held at an angle towards one wall) to each person, that they could walk around the table lamp to show how the sunlight fell more on one hemisphere then the other.

I know how to do that, it’s just in my house that I’m thinking. We have a light up globe, I just thought it would be cool to make it work differently. With modern LEDs I’m sure you could make it happen.

You could actually buy one, a little while ago, but it has been discontinued. It was the Elenco Night & Day Globe. It seems to be not very easy, which is why this is the only model I have found, even in specialist globe retailers, and it has been discontinued. But you can look at this manual and perhaps gain some clues from the mechanism it depicts.

With a globe that is lit externally, you would need the light to be at some distance from the globe to present a sharp day/night terminator. The light could remain in a fixed location, but you'd have to generate the seasons by rotating the globe base so that the axis rotated relative to the light.

With a globe that lights up in the interior, what you'd really need would be an internal light-proof vertical partition, with a light on one side of it, to separate day and night. But as it would turn on a different axis from the external globe's axis, that would be bit tricky to arrange. Maybe there'd be some trick with something that looks a bit like the mechanism of a maritime self-levelling compass, but with pivots at an angle of 23 degrees rather than 90 degrees, you'd have in the interior to organise it. Or maybe you'd some kind of a channel around the antarctic circle, as some point of the antarctic circle would always be at the lowest point, that the axis would pierce through. Though if you can rotate something all the way around the antarctic circle, how does the globe avoid falling into two pieces. In fact, having a look at that Elenco globe manual, basically they don't have anything south of the antarctic circle. They rotate the upper part of the globe around the blank antarctic circle piece. There is a partition inside the globe with a bright light on one side of it. The partition rotates around a vertical axis that is fixed to one edge of this fixed antarctic circle part.

It strikes me that you could alternatively have an external hemisphere, which covers over the night side, to separate them. But it would need some kind of provision that the fixing for the globe's own axis could move through it, when the south pole was in antarctic summer, for example. So that would also be awkward, but again maybe something that looks a bit like a self-levelling compass would achieve it.

You could in principle stud the globe with lots of little LEDs, but you'd need a computer program to select them.

Thanks, that’s exactly the kind of thing. Yes, I realised having two different axes would be tricky, which is why I thought about using LEDs. If the internal surface was evenly covered in LEDs then it couldn’t be all that hard to write a program on a Raspberry Pi or similar to switch on the lights that simulate sunlight at a particular day and time. Or go one step further and make a globe shaped screen, then you could change the display to match Google Earth or whatever.

[dyqik]

I'd do it with a sphere inside a sphere, magnetically constrained by a stand, and powered wirelessly. The inner sphere would be half black, half lit.

You could probably even make it float.

[Gfamily]

Here's a great talk by the Astronomer Royal for Scotland, talking about some of the issues with Cosmology and how cosmologists are really looking for the rest of the astronomy community to help them understand what's behind the problems.

The talk is one of the Plenary Talks for the National Astronomy Meeting (currently taking place in Hull); however, as Catherine Heymans is one of the many sufferers with Long Covid, she had to give it remotely; which means it can be shared to a wider audience.

https://media.ed.ac.uk/media/NAM+2024/1_9dmbfg5o

[Brightonian]

Selenological spelunking, anyone?
https://www.bbc.com/news/articles/ce784r9njz0o

[dyqik]

Selenological spelunking, anyone?
https://www.bbc.com/news/articles/ce784r9njz0o

It sounds safer than cave diving...

[Boustrophedon]

Not strictly astronomy, but is there such a thing as a globe that illuminates half the surface to allow you to show how the seasons work? I’m imagining a tilted globe but with the light terminator being vertical, so that when you spin it, it simulates the day light at a particular time of year. You would have to be able to move the light around to change the time of year.

Not seen a 3D one but bizarrely there is a 2D map clock that shows a map of the world with day and night and the changes with the seasons. Needless to say, I want one.
https://www.geochron.com/

[Grumble]

Not strictly astronomy, but is there such a thing as a globe that illuminates half the surface to allow you to show how the seasons work? I’m imagining a tilted globe but with the light terminator being vertical, so that when you spin it, it simulates the day light at a particular time of year. You would have to be able to move the light around to change the time of year.

Not seen a 3D one but bizarrely there is a 2D map clock that shows a map of the world with day and night and the changes with the seasons. Needless to say, I want one.
https://www.geochron.com/

Why didn’t you link this before my birthday? Honestly. I’ll have to wait till Christmas now. $500 though, might need to save up for that one.

[Boustrophedon]

Why didn’t you link this before my birthday? Honestly. I’ll have to wait till Christmas now. $500 though, might need to save up for that one.

The mechanical one is £3K

[Grumble]

Why didn’t you link this before my birthday? Honestly. I’ll have to wait till Christmas now. $500 though, might need to save up for that one.

The mechanical one is £3K

Yeah, no

[dyqik]

A 4K TV, a RPi and a screensaver would be cheaper.

[Gfamily]

Why didn’t you link this before my birthday? Honestly. I’ll have to wait till Christmas now. $500 though, might need to save up for that one.

The mechanical one is £3K

Yeah, no

I refrained from suggesting you could program a Raspberry Pi to display one on a cheap display.
But if you have a techy young relative, she may be appreciative of having a project - would look good on an application form*

*gfamdottir wrote her own IRC client in the downtime after Uni and I'm sure it helped her job search.

[Boustrophedon]

I refrained from suggesting you could program a Raspberry Pi to display one on a cheap display.

The same could be said of any of my clocks, they could be replaced by a display, but that's really not the point. The mechanical Geochron has gears and levers and cam controlled bendy shades to cast the shadows, an electronic display is just not the same. I hate to come over all 'Clarkson talking about an Alfa Romeo' but it's got no soul.

[Gfamily]

I refrained from suggesting you could program a Raspberry Pi to display one on a cheap display.

The same could be said of any of my clocks, they could be replaced by a display, but that's really not the point. The mechanical Geochron has gears and levers and cam controlled bendy shades to cast the shadows, an electronic display is just not the same. I hate to come over all 'Clarkson talking about an Alfa Romeo' but it's got no soul.

Huh, so Dyqik gets away with it, but my personal family history 'has no soul' - I can tell you, young man* - if I was less sozzled on a Sunday evening, I would be less offended

* modify adjective and noun as appropriate.

Oh, and Grumble thanks you for the kind offer and wonders when they can come round to pick it up

[Boustrophedon]

Huh, so Dyqik gets away with it, but my personal family history 'has no soul' - I can tell you, young man* - if I was less sozzled on a Sunday evening, I would be less offended

* modify adjective and noun as appropriate.

My apologies for picking on you particularly, I could have included both quotes, I usually never pass up a chance for a dig at Dyqik.

[dyqik]

Direct imaging of an exoplanet from JWST.

https://badastronomy.beehiiv.com/p/jwst ... -exoplanet

[JQH]

The mass and distance fron Epsilon Indi A are quite different from those calculated by indirect means. Makes me wonder how accurate our pictures of other planetary dydtems actually are.

[Gfamily]

The mass and distance fron Epsilon Indi A are quite different from those calculated by indirect means. Makes me wonder how accurate our pictures of other planetary dydtems actually are.

The majority of other exoplanetary systems are identified by the transit method, which allows to give a relatively reliable number for the period, and given what we know about stellar evolution we should be able to get a reasonable number for the Mass of the star, hence we can calculate a reasonably reliable for value for the orbit size (though not necessarily how elliptical it is).
For this system, which is not a transit case, you are relying on small variations in the doppler shift and the variations from a precise 'straight line*' proper motion through space to determine the orbit, so the uncertainties will be higher.

So in most cases, we should be able to be more confident

* in this case, not a 'straight line' because of the influence of the binary brown dwarf stars that orbit it.

[dyqik]

In any case, "astronomical precision" is traditionally "to within a couple of orders of magnitude". There's even a unit for that, which I only recently learned about - the 'dex', for 'decimal exponent'.

So ±2 dex means "between 100x and 0.01x"

[Gfamily]

I don't know if anyone has some 'eclipse glasses' but, if you do - it'll be worth checking out the Sun tomorrow, as there's a very large sunspot group at the moment that should be (protected) naked eye visible.

ar3780 Group.jpg (113.74 KiB) Viewed 1835 times

[Gfamily]

I don't know if anyone has some 'eclipse glasses' but, if you do - it'll be worth checking out the Sun tomorrow, as there's a very large sunspot group at the moment that should be (protected) naked eye visible.
ar3780 Group.jpg

And now there are two naked eye sunspots - I can't remember the last time they were two...

reduced_1000009749.jpg (8.72 KiB) Viewed 1203 times

[dyqik]

And now there are two naked eye sunspots

Reminder: do not try to stare at sunspots with your remaining naked eye.