SKU: 43433768887

Radiometer - Impress the In-Laws...Leave it by a Window*

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Ships within 48 hours · Estimated delivery Aug 8 - Aug 13

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Description

Radiometer - Impress the In-Laws...Leave it by a Window*Experience a classic Crookes radiometer for yourself! The metal inside the sealed glass will spin when exposed to strong light. Leave it by a window on a sunny day the stronger the light, the faster it spins! Why does it turn you ask? Well, in case anyone asks, a common myth (one originally held even by the scientist who invented it in 1873, Sir William Crookes) is that the momentum of the absorbed light on the black faces makes the radiometer

Experience a classic Crookes radiometer for yourself!  The metal inside the sealed glass will spin when exposed to strong light.  Leave it by a window on a sunny day...the stronger the light, the faster it spins!

Why does it turn you ask?  Well, in case anyone asks, a common myth (one originally held even by the scientist who invented it in 1873, Sir William Crookes) is that the momentum of the absorbed light on the black faces makes the radiometer operate.  But this can't be right because the white faces move forward (not away from) towards the light source.  Photons of light do exert radiation pressure on the faces, but other effects dwarf these forces. The final explanation it seems depends on having just the right degree of vacuum and is more related to the flow of heat than the direct effect of photons.

For the more adventurous, try out the Precision model.  They are handmade in Germany and are incredibly sensitive, spinning at up to 3,000 rpm in bright sunlight.  With a bit of patience, it will even respond to just the infrared radiation from the heat of your hand!

Recommended for Age 12 & Up (with adult supervision)

*  Especially if you can be nonchalant about it...

 

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Exchange/Return Notes
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SKU: 43433768887

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4.3 ★★★★★
Based on 17 reviews
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Irene Z.
Boise, US
★★★★★ 5
Love these
Size: 18-24 Months Infant, Color: Grey
These are awesome! My 15-month old wore these everywhere on our trip to Mexico. He scuffed them up quite a bit, but other than cosmetics, they're holding strong through sand, sprinklers, and general gallivanting around. They are super easy to get on, which also makes them easy for him to pull off. But as long as he's busy running a muck, he forgets they're even on his feet.
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Reviewed in the United States on January 21, 2026
N
Verified Purchase
NAZIK
Massapequa, US
★★★★★ 4
Sizing is off, send me free pair!
Size: 3-4 Years Toddler, Color: Navy, Size: 3-4 Years Toddler, Color: Navy
Sizing is off. I’m very frustrated. I ordered it to Costa Rica thru shipping company in Miami, which takes about 3 weeks to deliver and + shipping fee that they apply (20$) I spent time and checked the size guide. According to the size guide, I ordered “3-4 years old” which supposed to be 16cm from heel to toe) the pair I ordered ended up being 17cm! My baby’s feet are 15cm, I was planning to get 16cm for him to grow into it, but 17cm is too big. The shoes it self looks good, the leather is very soft and nice. I’m not sure how durable they are. Ordering first time from this brand. I ordered 2 pairs of shoes from a similar brand and liked it. They just didn’t have the size I needed. Although, the leather the previous brand uses for shoes seems much thicker. Again, I don’t know how durable “Dooty Fish” but I like how soft on skin they are.
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Reviewed in the United States on August 21, 2024
A
Verified Purchase
Amazon Customer
Boise, US
★★★★★ 5
Wide and flexible
Size: 18-24 Months Toddler, Color: White
Very cute I love the width and flexibility of the shoe 18 to 24 month is a bit too big for my 18 month old and she generally wears a size 6 1/2 shoe. I’m going to try the smaller size.
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Reviewed in the United States on July 15, 2025
K
Verified Purchase
Kelsey
Boise, US
★★★★★ 1
Don’t buy
Size: 12-18 Months Infant, Color: Navy
Cute little shoes but I would not recommend people buy these. The elastic broke on both shoes within a month. And they cannot get even a tiny bit of water on them. (Which is impossible with a toddler) If they do get wet the bottoms become dangerously slick. I wanted to get nice little barefoot shoes that I could use as hand-me-downs for future kiddos but these were not it. Horrible quality and not worth the money.
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Reviewed in the United States on August 23, 2025
F
Verified Purchase
Flora
Chelsea, US
★★★★★ 3
Quality control?
Size: 6-12 Months Infant, Color: Navy, Size: 6-12 Months Infant, Color: Navy
These were true to color (in blue) and are a cute design, however we received a pair that was oddly mismatched size-wise. They were both 6-12mo, however one moccasin was visibly larger and wider than the other. They were both too big for my 7mo old, but even when he'd grow into one the other would be much too large so we returned. Too bad because these would have been perfect if the quality control was there.
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Reviewed in the United States on July 13, 2025

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