## Is there a practical way to create/inject some visible interference into a nearby AC mains?

I have this 230 to 6V rms step-down transformer. I use it to observe the mains voltage.

But recently I needed to create some interference or spike in the mains. So I first tried the following:

I used a filterless power strip. I coupled the transformer’s primary side to one of the sockets of the power strip. And at the adjacent socket I plugged a heat gun. I sometimes very randomly saw some tiny fluctuation and that disappeared.

My approach was to see the interference from the nearby AC socket. What type of load would create a visible interference or spike? Or is there any other practical way to achieve this. I want to create a spike or interference by a load and observe that from a nearby AC socket via a scope and a transformer.

More over is there a safe way to observe the Line to earth or neutral to earth voltage? I mean if I use the transformer secondary for the line can I connect the scope ground to the mains earth safely? Or it is not possible?

## How will nearby galaxies some day expand beyond our horizon? (Neil deGrasse Tyson)

In his appearance on Television contained in the video The Mystery That Keeps Neil deGrasse Tyson Up At Night, Astronomer andeducator Neil deGrasse Tyson says:

I donât want to be blamed if you can not get to sleep tonight.

This dark energy, in the future, will render the universe so large, having accelerated so significantly, that all the galaxies of the night sky will have accelerated beyond our horizon.

All the galaxies are the source of our knowledge of the big bang.

Everything we know about the history of the universe comes to us from these galaxies.

If they accelerate beyond our horizon, the next generation of cosmic explorers will only have the stars of the milky way to think about.

What does this mean, in simple terms if possible. How will nearby galaxies some day expand beyond our horizon (if that’s what he’s saying and if it is correct)?

## Improve performance of this query finding nearby locations

I am trying to execute this SQL, but the query is really slow (almost 2 hours), It’s actually querying 1 million records (property_ids), that’s why it’s slow. But can someone suggest me a strategy to make this query faster, may be doing this in batches etc.

WITH properties AS
(SELECT sid FROM prod.vw_property WHERE status = 'active')
SELECT p.sid,
-- active list count means not expired
count(*) FILTER (WHERE cl.expired_at IS NULL) AS list_count_active,

-- 30d list count DOES include those that are now expired (ie. listed and expired quickly within 30d)
count(*) FILTER (WHERE (cl.listed_on >= ((now())::date - '30 days'::interval))) AS list_count_30d,

-- All other aggregates should only include active (not expired) rew listings
avg(cl.list_price) FILTER (WHERE cl.expired_at IS NULL) AS list_price_avg,
percentile_cont(0.50) WITHIN GROUP (ORDER BY cl.list_price) FILTER (WHERE cl.expired_at IS NULL)::numeric(12, 2) AS list_price_median,
min(cl.list_price) FILTER (WHERE cl.expired_at IS NULL) AS list_price_min,
max(cl.list_price) FILTER (WHERE cl.expired_at IS NULL) AS list_price_max,
avg((cl.list_price / (cl.interior_size_sqft)::numeric)) FILTER (WHERE (cl.interior_size_sqft > 100 AND cl.expired_at IS NULL)) AS list_price_per_sqft_avg,
percentile_cont((0.50)::double precision) WITHIN GROUP (ORDER BY (((cl.list_price / (cl.interior_size_sqft)::numeric))::double precision))
FILTER (WHERE (cl.interior_size_sqft > 100) AND cl.expired_at IS NULL)::numeric(12, 2) AS list_price_per_sqft_median,

-- Show up to 10 closest listings that were used to get the aggregate numbers
(array_agg(cl.rew_properties_id ORDER BY (st_distance(p.location, cl.location)))
FILTER (WHERE cl.expired_at IS NULL))[1:10] AS closest_rew_properties_ids
FROM prod.vw_property p
INNER JOIN prod.vw_comparable_listing cl
ON
((((COALESCE(upper(p.land_area_sqft), 0))::numeric >= cl.land_size_sqft_lower)
AND ((COALESCE(upper(p.land_area_sqft), 0))::numeric <= cl.land_size_sqft_upper)
AND (((upper(p.interior_area_finished_sqft))::numeric >= cl.interior_size_sqft_lower)
AND ((upper(p.interior_area_finished_sqft))::numeric <= cl.interior_size_sqft_upper))
AND (((p.num_bed)::numeric >= cl.num_bed_lower) AND ((p.num_bed)::numeric <= cl.num_bed_upper))
-- Within 2km
AND st_dwithin(p.location, cl.location, 2000) AND (
CASE
WHEN (p.rew_property_type = ANY (ARRAY['duplex'::prod.rew_property_type_enum, 'fourplex'::prod.rew_property_type_enum, 'triplex'::prod.rew_property_type_enum])) THEN 'townhouse'::prod.rew_property_type_enum
ELSE p.rew_property_type
END = cl.property_type_group)))
JOIN properties ps ON ps.sid = p.sid
GROUP BY 1;

Any suggestion will be appreciated. Also would like to add that AWS RDS large instance was at 52% due to this query.

Here is the Query plan:

QUERY PLAN
GroupAggregate  (cost=26994787.36..26994787.70 rows=1 width=212)
Group Key: p.sid
CTE properties
->  Seq Scan on property p_1  (cost=0.00..1260715.24 rows=2807666 width=4)
Filter: ((latitude IS NOT NULL) AND (longitude IS NOT NULL) AND (rew_geographies_id IS NOT NULL) AND (status = 'active'::prod.source_record_status_type))
->  Sort  (cost=25734072.12..25734072.13 rows=1 width=122)
Sort Key: p.sid
->  Nested Loop  (cost=0.54..25734072.11 rows=1 width=122)
Join Filter: (p.sid = ps.sid)
->  Nested Loop Left Join  (cost=0.54..25642822.97 rows=1 width=122)
Join Filter: (pt.sid = p.property_type_sid)
"                    Filter: (CASE WHEN (pt.rew_property_type = ANY ('{duplex,fourplex,triplex}'::prod.rew_property_type_enum[])) THEN 'townhouse'::prod.rew_property_type_enum ELSE pt.rew_property_type END = cl.property_type_group)"
->  Nested Loop  (cost=0.54..25641727.79 rows=36 width=130)
->  Seq Scan on vw_comparable_listing cl  (cost=0.00..881.04 rows=28404 width=100)
->  Index Scan using property_location_ix on property p  (cost=0.54..902.71 rows=1 width=96)
"                                Index Cond: (location && _st_expand(cl.location, '2000'::double precision))"
"                                Filter: ((latitude IS NOT NULL) AND (longitude IS NOT NULL) AND (rew_geographies_id IS NOT NULL) AND ((num_bed)::numeric >= cl.num_bed_lower) AND ((num_bed)::numeric <= cl.num_bed_upper) AND ((COALESCE(upper(land_area_sqft), 0))::numeric >= cl.land_size_sqft_lower) AND ((COALESCE(upper(land_area_sqft), 0))::numeric <= cl.land_size_sqft_upper) AND ((upper(interior_area_finished_sqft))::numeric >= cl.interior_size_sqft_lower) AND ((upper(interior_area_finished_sqft))::numeric <= cl.interior_size_sqft_upper) AND (cl.location && _st_expand(location, '2000'::double precision)) AND _st_dwithin(location, cl.location, '2000'::double precision, true))"
->  Materialize  (cost=0.00..57.41 rows=1361 width=8)
->  Seq Scan on property_type pt  (cost=0.00..50.61 rows=1361 width=8)
->  CTE Scan on properties ps  (cost=0.00..56153.32 rows=2807666 width=4)

## Is there any reference links to know learn to make a website to find nearby places in google maps by using…

I am developing a website to find nearby locations.I want to show user to find nearby locations that url links in my MySQL database according to their current locations.So can anyone suggest me a blog,video or any reference link to learn how to make it.

## Haunted television set summons zombies from nearby graves

I watched the Goosebumps movie tonight with my son and I started feeling nostalgic about other books (not in the Goosebumps series) that I read when I was a kid. I’ve been scouring Google looking for this one book for the last hour or so, and I can’t seem to find what I’m looking for.

I’m trying to figure out the title of one particular book from roughly the early 1990s. It must have been aimed at younger readers, because I recall checking it out from my elementary school library.

I think this book may have had a couple different stories in it. I don’t recall the other stories because, frankly, they were kind of lame. But this story really scared me at the time. This was, I believe, the first story in the book.

The story was about an old television set, complete with a channel knob. The the protagonist of the story was, I believe, a younger person – a boy. I don’t remember much of the “flesh” of the story, but here’s the gist of it…

As the kid was flipping through channels on the TV late at night, he came across what looked like a cemetery scene in some grainy old black and white horror movie. He thought the cemetery looked familiar, and at that point, he noticed that it looked a lot like a nearby cemetery. As he continued to watch, the TV then showed the dead rising out of their graves in the cemetery. Wondering what he was watching, the kid noticed that the knob of the TV was stuck between two different channels. As the kid continued to watch, the TV showed zombies shambling down the road outside the cemetery, and then down his road, and then outside of a house – his house. The zombies began pounding at the door of the house on the TV, and at the same time, the kid could hear pounding at his front door.

I believe the story may have ended with the kid disabling the TV somehow (unplugging it?), and the pounding at the door stopped.

Again, just for clarification, this was not a Goosebumps book. I don’t even know who the publisher was – if I had to guess, I’d have to say “Scholastic”? All I’m looking for is a title, either of the story or of the book itself.

## How will nearby galaxies some day expand beyond our horizon? (Neil deGrasse Tyson)

In his appearance on Television contained in the video The Mystery That Keeps Neil deGrasse Tyson Up At Night, Astronomer andeducator Neil deGrasse Tyson says:

I donât want to be blamed if you can not get to sleep tonight.

This dark energy, in the future, will render the universe so large, having accelerated so significantly, that all the galaxies of the night sky will have accelerated beyond our horizon.

All the galaxies are the source of our knowledge of the big bang.

Everything we know about the history of the universe comes to us from these galaxies.

If they accelerate beyond our horizon, the next generation of cosmic explorers will only have the stars of the milky way to think about.

What does this mean, in simple terms if possible. How will nearby galaxies some day expand beyond our horizon (if that’s what he’s saying and if it is correct)?

## PIR motion sensor interference by nearby CFL

I have a Passive Infrared Motion Detector (this one) in my walk-in closet that turns on the light when someone walks in. This setup has been working fine for many years.

Outside of the closet is my wife’s make-up area that was illuminated by a 75W incandescent ceiling light controlled by an on/off switch. No electronics here.

Because the 75W bulb was not bright enough, I replaced it with a 42W Compact Fluorescent Light whith a 150W equivalency rating. Now, when she walks into the closet when the CFL on, the light in the closet stays off. She has turn off the CFL for the motion sensor to work. When she turns the CFL back on, the light in the closet eventually times out like normal.

I cannot replace the CFL with a 150W incandescent bulb, since the bulb fitting is rated 100W max and 150W equivalent LEDS are too expensive (and big).

Any ideas?

## How will nearby galaxies some day expand beyond our horizon? (Neil deGrasse Tyson)

In his appearance on Television contained in the video The Mystery That Keeps Neil deGrasse Tyson Up At Night, Astronomer andeducator Neil deGrasse Tyson says:

I donât want to be blamed if you can not get to sleep tonight.

This dark energy, in the future, will render the universe so large, having accelerated so significantly, that all the galaxies of the night sky will have accelerated beyond our horizon.

All the galaxies are the source of our knowledge of the big bang.

Everything we know about the history of the universe comes to us from these galaxies.

If they accelerate beyond our horizon, the next generation of cosmic explorers will only have the stars of the milky way to think about.

What does this mean, in simple terms if possible. How will nearby galaxies some day expand beyond our horizon (if that’s what he’s saying and if it is correct)?