Fox has said it will be patient with “Utopia” — an expensive new reality show scheduled to air twice a week on the net this fall — but the show’s early ratings haven’t been encouraging.

The social-experiment series from the creator of “Big Brother” drew solid-enough sampling when slotted behind NFL action on Sunday, but viewership tailed off steadily during the course of the episode and then tumbled when it moved to its regular Tuesday timeslot. “Utopia” also hasn’t been much of a social-media dynamo.

As the show heads into its third episode tonight, Fox will be hoping to hook some new viewers. Although television viewing levels are lower on Fridays, tonight will be the first time “Utopia” doesn’t have to go up against CBS’ “Big Brother,” which would figure to share some audience with the Fox newbie; the competition tonight includes repeats on ABC and NBC and a special “48 Hours” on CBS.

Fox has slotted “Utopia” for two hours on the sked where it would do relatively minor damage to the net’s overall average. Friday at 8, where it’s slated to air for six weeks, is a low-profile. lightly watched timeslot, and expectations can’t be all that high on Tuesday at 8, where it will go up against the likes of ratings juggernauts “NCIS” and “The Voice.”

Looking at its early numbers, “Utopia” opened with a decent 2.0 rating/6 share in adults 18-49 and 4.63 million viewers overall from 8 to 10 p.m. when it followed the network’s high-rated NFL game and post-game coverage on Sunday.

Two nights later, it settled for a 0.9 rating/3 share in adults 18-49 and 2.48 million viewers overall in the 8 o’clock hour — a bit below the lower-tier reality shows “Extreme Weight Loss” on ABC (1.0 demo rating, 3.92 million total viewers for the hour) and “Food Fighters” on NBC (1.0, 4.35 million), both of which were airing their finales. “Big Brother” ruled the hour (2.3 demo rating, 6.76 million total viewers).

“Utopia” brings together 15 people to start a new world for themselves from scratch. Fox began live-streaming the cast prior to its Sunday premiere, generating more than 1 million streams in the first four days, according to the network, and the plan is to air it in some capacity 24/7 for a year.

How long Fox continues to broadcast “Utopia” figures to hinge on how it fares over the next couple of weeks. The net has a natural “out” come late October, as the World Series schedule includes games on Tuesday and Friday, so that may be an opportunity to yank it and start over with something new that can be promoted during baseball.

But if it continues to deliver sub-1 demo ratings, that decision could come sooner.

Fox did get some good news on the “Utopia” ratings front Friday, as updated Nielsen estimates for Sunday’s two-hour preview episode show that even more people watched than the network had expected. In Nielsen’s “live plus-3” data (three days’ worth of DVR playback), “Utopia” grew its 18-49 rating by 20% (2.4 vs. 2.0) and its overall audience by 19% (5.53 million vs. 4.63 million).

Fox had projected a DVR lift of about 10%, but more people may have put it on their DVR than expected because the first episode went up against the season premiere of NBC’s “Sunday Night Football.”