## Thursday, 2 July 2020

### The BBC does science, but they are useless at maths

From the BBC:

Astronomers have found a previously unseen type of object circling a distant star. It could be the core of a gas world like Jupiter, offering an unprecedented glimpse inside one of these giant planets...

Its radius is about three-and-a-half times larger than Earth's but the planet is around 39 times more massive.

Woah! Why "but" and not "and"??

The formula for the volume of a sphere = 4/3 x pi x radius cubed.

Therefore a planet with three-and-a-half times the radius of earth has 43 times the volume.

If a planet has 43 times the volume of Earth and 39 times the mass, we can safely assume it has a pretty similar density to Earth.
---------------------------------------------
Screenshot attached just in case they correct the glaring mistake:

decnine said...

I invoke the ghost of Archimedes. The Earth is a "rocky" planet and has a much higher density than Jupiter which is a "gaseous" planet. If this 'previously unseen' object has the same density as the Earth, it's very unlikely to be a gaseous planet.

D, the article says that the clever scientists think this is the left over core of a gas giant that has lost its gas, rather than a rocky planet. I've no idea how they work that out, but hey.

Ralph Musgrave said...

At the core of big gas planets like Saturn and Jupiter, pressures are so immense that density is similar to that of rock I believe. But if one removed the less dense outer layers of those planets, then presumably the core would expand and just form a new not so dense atmosphere. I'm puzzled.

A K Haart said...

I make that about 180 times the volume of the earth.

A K Haart said...

No I don't. I must work for the BBC.

RM of course. To return to my favourite topic, the centres of gas giants are insanely hot purely due to atmospheric pressure, even the outer surface of the atmosphere gets vary little sunlight and the centres get precisely none.

Which also explains why the earth's harder surface is 33 degrees warmer than it would be from sunlight alone. But the Alarmists don't want you to know that.

AKH, I hope you can get a ratio of about 43 with a bit of trial and error.

Dinero said...

Volumes can be tricky. The Pernod shot glass for example.

RM of course. To return to my favourite topic, the centres of gas giants are insanely hot purely due to atmospheric pressure, even though the outer surface of the atmosphere gets very little sunlight and the centres get precisely none.

Which also explains why the earth's harder surface is 33 degrees warmer than it would be from sunlight alone. But the Alarmists don't want you to know that.

AKH, I hope you can get a ratio of about 43 with a bit of trial and error.

Din, yes, their numbers seemed odd to me so I checked on a calulator. With shot glasses, just see how many times you can fill one up from a full bottle.

Dinero said...

The Pernod shot glass is an interesting example because it is shaped like the bell of a trumpet, and so a short measure by height in a Pernod glass is a very short measure by volume maybe half.

mombers said...

Poorly worded but not a mistake. They are saying that a plant of that size should be a lot lighter, rather than similar density to earth